diff --git a/admin_classes.php b/admin_classes.php
index 8aa8578..0ce16bc 100644
--- a/admin_classes.php
+++ b/admin_classes.php
@@ -17,7 +17,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['delete_id'])) {
         $stmt->execute([$delete_id, $school_id]);
         $message = "Class deleted successfully.";
     } catch (PDOException $e) {
-        $error = "Error deleting class: " . $e->getMessage();
+        if ($e->getCode() == '23000') { // Integrity constraint violation
+            $error = "Cannot delete this class because it has subjects, workloads, or schedules associated with it. Please remove those associations before deleting.";
+        } else {
+            $error = "Error deleting class: " . $e->getMessage();
+        }
     }
 }
 
diff --git a/admin_elective_groups.php b/admin_elective_groups.php
index cdbde86..c9d5144 100644
--- a/admin_elective_groups.php
+++ b/admin_elective_groups.php
@@ -17,7 +17,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['delete_id'])) {
         $stmt->execute([$delete_id, $school_id]);
         $message = "Elective group deleted successfully.";
     } catch (PDOException $e) {
-        $error = "Error deleting group: " . $e->getMessage();
+        if ($e->getCode() == '23000') { // Integrity constraint violation
+            $error = "Cannot delete this elective group because it has subjects associated with it. Please remove those associations before deleting.";
+        } else {
+            $error = "Error deleting group: " . $e->getMessage();
+        }
     }
 }
 
diff --git a/admin_subjects.php b/admin_subjects.php
index aa35195..662da2a 100644
--- a/admin_subjects.php
+++ b/admin_subjects.php
@@ -17,7 +17,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['delete_id'])) {
         $stmt->execute([$delete_id, $school_id]);
         $message = "Subject deleted successfully.";
     } catch (PDOException $e) {
-        $error = "Error deleting subject: " . $e->getMessage();
+        if ($e->getCode() == '23000') { // Integrity constraint violation
+            $error = "Cannot delete this subject because it is currently used in workloads or schedules. Please remove those associations before deleting.";
+        } else {
+            $error = "Error deleting subject: " . $e->getMessage();
+        }
     }
 }
 
diff --git a/admin_teachers.php b/admin_teachers.php
index c55fb63..3f22fba 100644
--- a/admin_teachers.php
+++ b/admin_teachers.php
@@ -29,7 +29,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['delete_id'])) {
         $message = "Teacher deleted successfully.";
     } catch (PDOException $e) {
         $pdo->rollBack();
-        $error = "Error deleting teacher: " . $e->getMessage();
+        if ($e->getCode() == '23000') { // Integrity constraint violation
+            $error = "Cannot delete this teacher because they are assigned to workloads or schedules. Please remove those associations before deleting.";
+        } else {
+            $error = "Error deleting teacher: " . $e->getMessage();
+        }
     }
 }
 
diff --git a/admin_timeslots.php b/admin_timeslots.php
index 5e5673c..82d716b 100644
--- a/admin_timeslots.php
+++ b/admin_timeslots.php
@@ -32,7 +32,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                 $error = 'Failed to delete timeslot.';
             }
         } catch (PDOException $e) {
-            $error = 'Database error: ' . $e->getMessage();
+            if ($e->getCode() == '23000') { // Integrity constraint violation
+                $error = "Cannot delete this timeslot because it is currently used in schedules. Please remove those associations before deleting.";
+            } else {
+                $error = "Error deleting timeslot: " . $e->getMessage();
+            }
         }
     }
     if (isset($_POST['add_timeslot'])) {
diff --git a/db/migrations/020_create_elective_group_subjects_table.sql b/db/migrations/020_create_elective_group_subjects_table.sql
new file mode 100644
index 0000000..acecdbb
--- /dev/null
+++ b/db/migrations/020_create_elective_group_subjects_table.sql
@@ -0,0 +1,7 @@
+CREATE TABLE IF NOT EXISTS `elective_group_subjects` (
+  `elective_group_id` INT NOT NULL,
+  `subject_id` INT NOT NULL,
+  PRIMARY KEY (`elective_group_id`, `subject_id`),
+  FOREIGN KEY (`elective_group_id`) REFERENCES `elective_groups`(`id`) ON DELETE CASCADE,
+  FOREIGN KEY (`subject_id`) REFERENCES `subjects`(`id`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
\ No newline at end of file
diff --git a/db/migrations/021_create_elective_group_subjects_table.sql b/db/migrations/021_create_elective_group_subjects_table.sql
new file mode 100644
index 0000000..df415f9
--- /dev/null
+++ b/db/migrations/021_create_elective_group_subjects_table.sql
@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS elective_group_subjects (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    elective_group_id INT NOT NULL,
+    subject_id INT NOT NULL,
+    FOREIGN KEY (elective_group_id) REFERENCES elective_groups(id) ON DELETE CASCADE,
+    FOREIGN KEY (subject_id) REFERENCES subjects(id) ON DELETE CASCADE,
+    UNIQUE KEY (elective_group_id, subject_id)
+);
diff --git a/includes/navbar.php b/includes/navbar.php
new file mode 100644
index 0000000..842197e
--- /dev/null
+++ b/includes/navbar.php
@@ -0,0 +1,42 @@
+<?php
+// Note: This file assumes session_start() has been called by the including file.
+$current_page = basename($_SERVER['SCRIPT_NAME']);
+$role = $_SESSION['role'] ?? '';
+?>
+<nav class="navbar navbar-expand-lg navbar-light bg-white sticky-top shadow-sm">
+    <div class="container">
+        <a class="navbar-brand fw-bold" href="/">Haki Schedule</a>
+        <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
+            <span class="navbar-toggler-icon"></span>
+        </button>
+        <div class="collapse navbar-collapse" id="navbarNav">
+            <ul class="navbar-nav ms-auto">
+                <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'index.php') ? 'active' : ''; ?>" href="/">Home</a></li>
+                <?php if (isset($_SESSION['user_id'])) : ?>
+                    <?php if ($role === 'admin'): ?>
+                        <li class="nav-item dropdown">
+                            <a class="nav-link dropdown-toggle <?php echo (strpos($current_page, 'admin_') === 0) ? 'active' : ''; ?>" href="#" id="manageDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
+                                Manage
+                            </a>
+                            <ul class="dropdown-menu" aria-labelledby="manageDropdown">
+                                <li><a class="dropdown-item" href="/admin_classes.php">Classes</a></li>
+                                <li><a class="dropdown-item" href="/admin_subjects.php">Subjects</a></li>
+                                <li><a class="dropdown-item" href="/admin_teachers.php">Teachers</a></li>
+                                <li><a class="dropdown-item" href="/admin_workloads.php">Workloads</a></li>
+                                <li><a class="dropdown-item" href="/admin_timeslots.php">Timeslots</a></li>
+                                <li><a class="dropdown-item" href="/admin_elective_groups.php">Elective Groups</a></li>
+                            </ul>
+                        </li>
+                        <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'timetable.php') ? 'active' : ''; ?>" href="/timetable.php">Class Timetable</a></li>
+                    <?php endif; ?>
+                    <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'teacher_timetable.php') ? 'active' : ''; ?>" href="/teacher_timetable.php">Teacher Timetable</a></li>
+                    <li class="nav-item"><a class="nav-link" href="/logout.php">Logout</a></li>
+                <?php else : ?>
+                    <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'demo.php') ? 'active' : ''; ?>" href="/demo.php">Demo</a></li>
+                    <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'login.php') ? 'active' : ''; ?>" href="/login.php">Login</a></li>
+                    <li class="nav-item"><a class="nav-link <?php echo ($current_page == 'register.php') ? 'active' : ''; ?>" href="/register.php">Register</a></li>
+                <?php endif; ?>
+            </ul>
+        </div>
+    </div>
+</nav>
\ No newline at end of file
diff --git a/teacher_timetable.php b/teacher_timetable.php
index 07a7d9e..6007ac7 100644
--- a/teacher_timetable.php
+++ b/teacher_timetable.php
@@ -85,9 +85,9 @@ foreach ($timeslots as $timeslot) {
 }
 
 foreach ($teacher_schedule_raw as $lesson) {
-    $day_idx = $lesson['day_of_week'];
+    $day_idx = $lesson['day_of_week'] - 1; // Adjust for 0-based array index
     $timeslot_id = $lesson['timeslot_id'];
-    if (isset($teacher_timetable[$day_idx][$timeslot_id])) {
+    if (isset($teacher_timetable[$day_idx]) && isset($teacher_timetable[$day_idx][$timeslot_id])) {
         $teacher_timetable[$day_idx][$timeslot_id] = $lesson;
     }
 }
@@ -181,7 +181,7 @@ foreach ($teacher_schedule_raw as $lesson) {
                     <select name="teacher_id" id="teacher_id" class="form-select" onchange="this.form.submit()">
                         <option value="">-- Select a Teacher --</option>
                         <?php foreach ($teachers as $teacher): ?>
-                            <option value="<?php echo $teacher['id']; ?>" <?php echo ($selected_teacher_id == $teacher['id']) ? 'selected' : ''; ?>>
+                            <option value="<?php echo $teacher['id']; ?>" <?php echo ($selected_teacher_id == $teacher['id']) ? 'selected' : ''; ?> >
                                 <?php echo htmlspecialchars($teacher['name']); ?>
                             </option>
                         <?php endforeach; ?>
diff --git a/timetable.php b/timetable.php
index 363384e..654b302 100644
--- a/timetable.php
+++ b/timetable.php
@@ -4,370 +4,258 @@ require_once 'includes/auth_check.php';
 require_once 'db/config.php';
 
 // --- Database Fetch ---
-function get_workloads($pdo) {
-    $stmt = $pdo->query("
+function get_all_data($pdo) {
+    $data = [];
+    $data['classes'] = $pdo->query("SELECT * FROM classes ORDER BY name")->fetchAll(PDO::FETCH_ASSOC);
+    $data['subjects'] = $pdo->query("SELECT id, name FROM subjects")->fetchAll(PDO::FETCH_KEY_PAIR);
+    $data['teachers'] = $pdo->query("SELECT id, name FROM teachers")->fetchAll(PDO::FETCH_KEY_PAIR);
+    $data['timeslots'] = $pdo->query("SELECT * FROM timeslots ORDER BY start_time")->fetchAll(PDO::FETCH_ASSOC);
+    
+    $workloads_stmt = $pdo->query("
         SELECT 
-            w.id,
-            c.id as class_id,
+            w.class_id, w.subject_id, w.teacher_id, w.lessons_per_week,
+            s.name as subject_name, s.has_double_lesson, s.elective_group_id,
             c.name as class_name,
-            s.id as subject_id,
-            s.name as subject_name,
-            s.has_double_lesson,
-            s.elective_group_id,
-            eg.name as elective_group_name,
-            t.id as teacher_id,
             t.name as teacher_name,
-            w.lessons_per_week
+            eg.name as elective_group_name
         FROM workloads w
-        JOIN classes c ON w.class_id = c.id
         JOIN subjects s ON w.subject_id = s.id
+        JOIN classes c ON w.class_id = c.id
         JOIN teachers t ON w.teacher_id = t.id
         LEFT JOIN elective_groups eg ON s.elective_group_id = eg.id
-        ORDER BY c.name, s.name
     ");
-    return $stmt->fetchAll(PDO::FETCH_ASSOC);
+    $data['workloads'] = $workloads_stmt->fetchAll(PDO::FETCH_ASSOC);
+
+    return $data;
 }
 
-function get_classes($pdo) {
-    return $pdo->query("SELECT * FROM classes ORDER BY name")->fetchAll(PDO::FETCH_ASSOC);
-}
-
-function get_timeslots($pdo) {
-    return $pdo->query("SELECT * FROM timeslots ORDER BY start_time")->fetchAll(PDO::FETCH_ASSOC);
-}
-
-// --- Helper Functions ---
-function get_grade_from_class_name($class_name) {
-    if (preg_match('/^(Grade\s+\d+)/i', $class_name, $matches)) {
-        return $matches[1];
-    }
-    return $class_name;
-}
-
-// --- Scoring and Placement Logic ---
-function find_best_slot_for_lesson($lesson, $is_double, &$class_timetables, &$teacher_timetables, $all_class_ids, $days_of_week, $periods_per_day) {
-    $best_slot = null;
-    $highest_score = -1000;
-
-    $class_id = $lesson['type'] === 'horizontal_elective' ? null : $lesson['class_id'];
-    $teachers_in_lesson = array_unique(array_column($lesson['component_lessons'], 'teacher_id'));
-    $class_ids_in_lesson = $lesson['type'] === 'horizontal_elective' ? $lesson['participating_class_ids'] : [$class_id];
-
-    for ($day = 0; $day < count($days_of_week); $day++) {
-        for ($period = 0; $period < $periods_per_day; $period++) {
-            $current_score = 100; // Base score
-
-            // 1. Check basic availability
-            $slot_available = true;
-            if ($is_double) {
-                if ($period + 1 >= $periods_per_day) continue; // Not enough space for a double
-                foreach ($class_ids_in_lesson as $cid) {
-                    if (isset($class_timetables[$cid][$day][$period]) || isset($class_timetables[$cid][$day][$period + 1])) {
-                        $slot_available = false; break;
-                    }
-                }
-                if (!$slot_available) continue;
-                foreach ($teachers_in_lesson as $teacher_id) {
-                    if (isset($teacher_timetables[$teacher_id][$day][$period]) || isset($teacher_timetables[$teacher_id][$day][$period + 1])) {
-                        $slot_available = false; break;
-                    }
-                }
-            } else {
-                foreach ($class_ids_in_lesson as $cid) {
-                    if (isset($class_timetables[$cid][$day][$period])) {
-                        $slot_available = false; break;
-                    }
-                }
-                if (!$slot_available) continue;
-                foreach ($teachers_in_lesson as $teacher_id) {
-                    if (isset($teacher_timetables[$teacher_id][$day][$period])) {
-                        $slot_available = false; break;
-                    }
-                }
-            }
-            if (!$slot_available) continue;
-
-            // 2. Apply scoring rules
-            // A. Penalize placing the same subject on the same day
-            foreach ($class_ids_in_lesson as $cid) {
-                $lessons_on_day = 0;
-                for ($p = 0; $p < $periods_per_day; $p++) {
-                    if (isset($class_timetables[$cid][$day][$p]) && $class_timetables[$cid][$day][$p]['subject_name'] === $lesson['display_name']) {
-                        $lessons_on_day++;
-                    }
-                }
-                $current_score -= $lessons_on_day * 50; // Heavy penalty for each existing lesson of same subject
-            }
-
-            // B. Penalize creating gaps for teachers and classes
-            foreach ($teachers_in_lesson as $teacher_id) {
-                // Check for gap before the lesson
-                if ($period > 0 && !isset($teacher_timetables[$teacher_id][$day][$period - 1])) {
-                     if (isset($teacher_timetables[$teacher_id][$day][$period - 2])) $current_score -= 25; // Gap of 1
-                }
-                // Check for gap after the lesson
-                $after_period = $is_double ? $period + 2 : $period + 1;
-                if ($after_period < $periods_per_day && !isset($teacher_timetables[$teacher_id][$day][$after_period])) {
-                    if (isset($teacher_timetables[$teacher_id][$day][$after_period + 1])) $current_score -= 25; // Gap of 1
-                }
-            }
-            foreach ($class_ids_in_lesson as $cid) {
-                 if ($period > 0 && !isset($class_timetables[$cid][$day][$period - 1])) {
-                     if (isset($class_timetables[$cid][$day][$period - 2])) $current_score -= 10;
-                }
-                $after_period = $is_double ? $period + 2 : $period + 1;
-                if ($after_period < $periods_per_day && !isset($class_timetables[$cid][$day][$after_period])) {
-                    if (isset($class_timetables[$cid][$day][$after_period + 1])) $current_score -= 10;
-                }
-            }
-
-            // C. Penalize placing a double lesson of the same subject in parallel with another class
-            if ($is_double) {
-                $subject_name_to_check = $lesson['display_name'];
-                foreach ($all_class_ids as $cid) {
-                    if (in_array($cid, $class_ids_in_lesson)) continue; // Don't check against itself
-                    if (isset($class_timetables[$cid][$day][$period]) && $class_timetables[$cid][$day][$period]['is_double'] && $class_timetables[$cid][$day][$period]['subject_name'] === $subject_name_to_check) {
-                        $current_score -= 200; // Very high penalty for parallel doubles of same subject
-                        break;
-                    }
-                }
-            }
-
-            // D. Prefer ends of day for double lessons
-            if ($is_double) {
-                if ($period == 0 || $period + 1 == $periods_per_day -1) {
-                    $current_score += 10;
-                }
-            }
-
-            if ($current_score > $highest_score) {
-                $highest_score = $current_score;
-                $best_slot = ['day' => $day, 'period' => $period];
-            }
-        }
-    }
-
-    return $best_slot;
-}
 
 // --- Main Scheduling Engine ---
-function generate_timetable($workloads, $classes, $days_of_week, $periods_per_day) {
+function generate_timetable($data, $days_of_week) {
+    $periods = array_values(array_filter($data['timeslots'], function($ts) { return !$ts['is_break']; }));
+    $periods_per_day = count($periods);
+
+    // 1. Initialize Timetables
     $class_timetables = [];
-    foreach ($classes as $class) {
+    $teacher_timetables = [];
+    foreach ($data['classes'] as $class) {
         $class_timetables[$class['id']] = array_fill(0, count($days_of_week), array_fill(0, $periods_per_day, null));
     }
-    $teacher_timetables = [];
-
-    // --- Lesson Preparation ---
-    $all_lessons = [];
-    $workloads_by_grade_and_elective_group = [];
-
-    // 1. Group horizontal electives
-    foreach ($workloads as $workload) {
-        if (!empty($workload['elective_group_id'])) {
-            $grade_name = get_grade_from_class_name($workload['class_name']);
-            $workloads_by_grade_and_elective_group[$grade_name][$workload['elective_group_id']][] = $workload;
-        } else {
-            // This will be handled in the next step
-        }
+    foreach ($data['teachers'] as $teacher_id => $teacher_name) {
+        $teacher_timetables[$teacher_id] = array_fill(0, count($days_of_week), array_fill(0, $periods_per_day, null));
     }
 
-    $processed_workload_ids = [];
-    foreach ($workloads_by_grade_and_elective_group as $grade_name => $elective_groups) {
-        foreach ($elective_groups as $elective_group_id => $group_workloads) {
-            $participating_class_ids = array_unique(array_column($group_workloads, 'class_id'));
-            if (count($participating_class_ids) > 1) {
-                $first = $group_workloads[0];
-                $block = [
-                    'type' => 'horizontal_elective',
-                    'display_name' => $first['elective_group_name'],
-                    'participating_class_ids' => $participating_class_ids,
-                    'lessons_per_week' => $first['lessons_per_week'],
-                    'has_double_lesson' => $first['has_double_lesson'],
-                    'component_lessons' => $group_workloads,
-                    'priority' => 4 // Highest priority
+    // 2. Prepare Lessons
+    $lessons_to_schedule = [];
+    $electives_by_group_grade = [];
+
+    foreach ($data['workloads'] as $workload) {
+        if (empty($workload['elective_group_id'])) { // Regular lesson
+            for ($i = 0; $i < $workload['lessons_per_week']; $i++) {
+                $is_double = ($i == 0 && $workload['has_double_lesson'] && $workload['lessons_per_week'] >= 2);
+                $lessons_to_schedule[] = [
+                    'type' => 'single',
+                    'class_id' => $workload['class_id'],
+                    'subject_id' => $workload['subject_id'],
+                    'teacher_ids' => [$workload['teacher_id']],
+                    'display_name' => $workload['subject_name'],
+                    'teacher_name' => $workload['teacher_name'],
+                    'is_double' => $is_double,
+                    'is_elective' => false
                 ];
-                $all_lessons[] = $block;
-                foreach($group_workloads as $w) $processed_workload_ids[] = $w['id'];
+                if ($is_double) $i++;
             }
+        } else { // Elective lesson part
+            $grade = preg_replace('/[^0-9]/', '', $workload['class_name']);
+            $key = $workload['elective_group_id'] . '_grade_' . $grade;
+            if (!isset($electives_by_group_grade[$key])) {
+                $electives_by_group_grade[$key] = [
+                    'type' => 'elective_group',
+                    'display_name' => $workload['elective_group_name'] . " (Form " . $grade . ")",
+                    'lessons_per_week' => $workload['lessons_per_week'],
+                    'has_double_lesson' => $workload['has_double_lesson'],
+                    'is_elective' => true,
+                    'component_lessons' => []
+                ];
+            }
+            $electives_by_group_grade[$key]['component_lessons'][] = $workload;
         }
     }
 
-    // 2. Group remaining lessons (single, elective, and normal doubles)
-    $remaining_workloads = array_filter($workloads, function($w) use ($processed_workload_ids) {
-        return !in_array($w['id'], $processed_workload_ids);
+    foreach ($electives_by_group_grade as $group) {
+        for ($i = 0; $i < $group['lessons_per_week']; $i++) {
+            $is_double = ($i == 0 && $group['has_double_lesson'] && $group['lessons_per_week'] >= 2);
+            $class_ids = array_unique(array_column($group['component_lessons'], 'class_id'));
+            $teacher_ids = array_unique(array_column($group['component_lessons'], 'teacher_id'));
+            
+            $lessons_to_schedule[] = [
+                'type' => 'elective_group',
+                'class_id' => $class_ids, // Now an array of classes
+                'subject_id' => null, // Grouped subject
+                'teacher_ids' => $teacher_ids,
+                'display_name' => $group['display_name'],
+                'is_double' => $is_double,
+                'is_elective' => true,
+                'component_lessons' => $group['component_lessons']
+            ];
+            if ($is_double) $i++;
+        }
+    }
+    
+    // 3. Sort lessons (place doubles and electives first)
+    usort($lessons_to_schedule, function($a, $b) {
+        if ($b['is_double'] != $a['is_double']) return $b['is_double'] <=> $a['is_double'];
+        $a_count = is_array($a['class_id']) ? count($a['class_id']) : 1;
+        $b_count = is_array($b['class_id']) ? count($b['class_id']) : 1;
+        return $b_count <=> $a_count;
     });
 
-    $workloads_by_class = [];
-    foreach ($remaining_workloads as $workload) {
-        $workloads_by_class[$workload['class_id']][] = $workload;
-    }
-
-    foreach ($workloads_by_class as $class_id => $class_workloads) {
-        $elective_groups = [];
-        $individual_lessons = [];
-        foreach ($class_workloads as $workload) {
-            if (!empty($workload['elective_group_id'])) {
-                $elective_groups[$workload['elective_group_id']][] = $workload;
-            } else {
-                $individual_lessons[] = $workload;
-            }
-        }
-
-        foreach ($elective_groups as $group_id => $group_workloads) {
-            $first = $group_workloads[0];
-            $all_lessons[] = [
-                'type' => 'elective', 'class_id' => $class_id, 'display_name' => $first['elective_group_name'],
-                'lessons_per_week' => $first['lessons_per_week'], 'has_double_lesson' => $first['has_double_lesson'],
-                'component_lessons' => $group_workloads,
-                'priority' => 3
-            ];
-        }
-
-        foreach ($individual_lessons as $workload) {
-            $all_lessons[] = [
-                'type' => 'single', 'class_id' => $workload['class_id'], 'display_name' => $workload['subject_name'],
-                'lessons_per_week' => $workload['lessons_per_week'], 'has_double_lesson' => $workload['has_double_lesson'],
-                'component_lessons' => [$workload],
-                'priority' => $workload['has_double_lesson'] ? 2 : 1
-            ];
-        }
-    }
-
-    // 3. Explode lessons into single and double instances
-    $final_lesson_list = [];
-    foreach ($all_lessons as $lesson_block) {
-        $num_doubles = 0;
-        $num_singles = $lesson_block['lessons_per_week'];
-        if ($lesson_block['has_double_lesson'] && $lesson_block['lessons_per_week'] >= 2) {
-            $num_doubles = 1;
-            $num_singles -= 2;
-        }
-        for ($i=0; $i < $num_doubles; $i++) {
-            $final_lesson_list[] = ['is_double' => true, 'lesson_details' => $lesson_block];
-        }
-        for ($i=0; $i < $num_singles; $i++) {
-            $final_lesson_list[] = ['is_double' => false, 'lesson_details' => $lesson_block];
-        }
-    }
-
-    // 4. Sort by priority (desc) and then shuffle to vary timetable
-    usort($final_lesson_list, function($a, $b) {
-        $prio_a = $a['lesson_details']['priority'];
-        $prio_b = $b['lesson_details']['priority'];
-        if ($prio_a != $prio_b) return $prio_b - $prio_a;
-        if ($a['is_double'] != $b['is_double']) return $b['is_double'] - $a['is_double'];
-        return rand(-1, 1);
-    });
-
-    // --- Placement using Scoring ---
-    $all_class_ids = array_column($classes, 'id');
-
-    foreach ($final_lesson_list as $lesson_item) {
-        $lesson = $lesson_item['lesson_details'];
-        $is_double = $lesson_item['is_double'];
-        
-        $best_slot = find_best_slot_for_lesson($lesson, $is_double, $class_timetables, $teacher_timetables, $all_class_ids, $days_of_week, $periods_per_day);
+    // 4. Placement
+    foreach ($lessons_to_schedule as $lesson) {
+        $best_slot = find_best_slot_for_lesson($lesson, $class_timetables, $teacher_timetables, $days_of_week, $periods_per_day);
 
         if ($best_slot) {
             $day = $best_slot['day'];
             $period = $best_slot['period'];
-            $class_ids_to_place = ($lesson['type'] === 'horizontal_elective') ? $lesson['participating_class_ids'] : [$lesson['class_id']];
-            $teachers_to_place = array_unique(array_column($lesson['component_lessons'], 'teacher_id'));
+            
+            if ($lesson['type'] === 'single') {
+                $class_id = $lesson['class_id'];
+                $teacher_id = $lesson['teacher_ids'][0];
+                
+                $lesson_data = [
+                    'subject_name' => $lesson['display_name'],
+                    'teacher_name' => $lesson['teacher_name'],
+                    'subject_id' => $lesson['subject_id'],
+                    'teacher_ids' => $lesson['teacher_ids'],
+                    'is_double' => $lesson['is_double'],
+                    'is_elective' => false,
+                ];
 
-            $subject_id = null;
-            $teacher_id = null;
-            // For single-teacher, single-subject lessons, store the IDs directly
-            if (count($lesson['component_lessons']) === 1) {
-                $subject_id = $lesson['component_lessons'][0]['subject_id'];
-                $teacher_id = $lesson['component_lessons'][0]['teacher_id'];
-            }
-
-            $lesson_info = [
-                'subject_id' => $subject_id,
-                'teacher_id' => $teacher_id,
-                'subject_name' => $lesson['display_name'],
-                'teacher_name' => count($teachers_to_place) > 1 ? 'Multiple' : $lesson['component_lessons'][0]['teacher_name'],
-                'is_double' => $is_double,
-                'is_elective' => $lesson['type'] === 'elective',
-                'is_horizontal_elective' => $lesson['type'] === 'horizontal_elective',
-                'component_lessons' => $lesson['component_lessons']
-            ];
-
-            if ($is_double) {
-                foreach ($class_ids_to_place as $cid) {
-                    $class_timetables[$cid][$day][$period] = $lesson_info;
-                    $class_timetables[$cid][$day][$period + 1] = $lesson_info;
+                $class_timetables[$class_id][$day][$period] = $lesson_data;
+                $teacher_timetables[$teacher_id][$day][$period] = true;
+                if ($lesson['is_double']) {
+                    $class_timetables[$class_id][$day][$period + 1] = $lesson_data;
+                    $teacher_timetables[$teacher_id][$day][$period + 1] = true;
                 }
-                foreach ($teachers_to_place as $tid) {
-                    $teacher_timetables[$tid][$day][$period] = true;
-                    $teacher_timetables[$tid][$day][$period + 1] = true;
+            } else { // Elective Group
+                foreach($lesson['component_lessons'] as $comp_lesson) {
+                    $class_id = $comp_lesson['class_id'];
+                    $teacher_id = $comp_lesson['teacher_id'];
+
+                    $lesson_data = [
+                        'subject_name' => $comp_lesson['subject_name'],
+                        'teacher_name' => $comp_lesson['teacher_name'],
+                        'subject_id' => $comp_lesson['subject_id'],
+                        'teacher_ids' => [$teacher_id], // Specific teacher for this part
+                        'is_double' => $lesson['is_double'],
+                        'is_elective' => true,
+                        'group_name' => $lesson['display_name']
+                    ];
+
+                    $class_timetables[$class_id][$day][$period] = $lesson_data;
+                    $teacher_timetables[$teacher_id][$day][$period] = true;
+                    if ($lesson['is_double']) {
+                        $class_timetables[$class_id][$day][$period + 1] = $lesson_data;
+                        $teacher_timetables[$teacher_id][$day][$period + 1] = true;
+                    }
                 }
-            } else {
-                foreach ($class_ids_to_place as $cid) $class_timetables[$cid][$day][$period] = $lesson_info;
-                foreach ($teachers_to_place as $tid) $teacher_timetables[$tid][$day][$period] = true;
             }
         }
     }
+
     return $class_timetables;
 }
 
+function find_best_slot_for_lesson($lesson, &$class_timetables, &$teacher_timetables, $days_of_week, $periods_per_day) {
+    $is_double = $lesson['is_double'];
+    $class_ids = is_array($lesson['class_id']) ? $lesson['class_id'] : [$lesson['class_id']];
+    $teacher_ids = $lesson['teacher_ids'];
+
+    for ($day = 0; $day < count($days_of_week); $day++) {
+        for ($period = 0; $period < $periods_per_day; $period++) {
+            if ($is_double && $period + 1 >= $periods_per_day) continue;
+
+            // Check availability for all classes and teachers
+            $slot_available = true;
+            foreach ($class_ids as $cid) {
+                if ($class_timetables[$cid][$day][$period] !== null || ($is_double && $class_timetables[$cid][$day][$period + 1] !== null)) {
+                    $slot_available = false; break;
+                }
+            }
+            if (!$slot_available) continue;
+
+            foreach ($teacher_ids as $tid) {
+                if ($teacher_timetables[$tid][$day][$period] !== null || ($is_double && $teacher_timetables[$tid][$day][$period + 1] !== null)) {
+                    $slot_available = false; break;
+                }
+            }
+            
+            if ($slot_available) {
+                return ['day' => $day, 'period' => $period]; // Return first available slot (simplistic)
+            }
+        }
+    }
+    return null; // No slot found
+}
+
+
 // --- Timetable Persistence ---
 function save_timetable($pdo, $class_timetables, $timeslots) {
-    $pdo->exec('TRUNCATE TABLE schedules');
-    $pdo->exec('TRUNCATE TABLE schedule_teachers');
+    try {
+        $pdo->beginTransaction();
+        $pdo->exec('SET FOREIGN_KEY_CHECKS=0');
+        $pdo->exec('TRUNCATE TABLE schedule_teachers');
+        $pdo->exec('TRUNCATE TABLE schedules');
+        $pdo->exec('SET FOREIGN_KEY_CHECKS=1');
 
-    $stmt = $pdo->prepare(
-        'INSERT INTO schedules (class_id, day_of_week, timeslot_id, subject_id, lesson_display_name, teacher_display_name, is_double, is_elective, is_horizontal_elective) ' .
-        'VALUES (:class_id, :day_of_week, :timeslot_id, :subject_id, :lesson_display_name, :teacher_display_name, :is_double, :is_elective, :is_horizontal_elective)'
-    );
-    $teacher_stmt = $pdo->prepare(
-        'INSERT INTO schedule_teachers (schedule_id, teacher_id) VALUES (:schedule_id, :teacher_id)'
-    );
+        $stmt = $pdo->prepare(
+            'INSERT INTO schedules (class_id, day_of_week, timeslot_id, subject_id, lesson_display_name, teacher_display_name, is_double, is_elective) ' .
+            'VALUES (:class_id, :day_of_week, :timeslot_id, :subject_id, :lesson_display_name, :teacher_display_name, :is_double, :is_elective)'
+        );
+        $teacher_stmt = $pdo->prepare(
+            'INSERT INTO schedule_teachers (schedule_id, teacher_id) VALUES (:schedule_id, :teacher_id)'
+        );
 
-    $lesson_periods = array_values(array_filter($timeslots, function($ts) { return !$ts['is_break']; }));
+        $lesson_periods = array_values(array_filter($timeslots, function($ts) { return !$ts['is_break']; }));
 
-    foreach ($class_timetables as $class_id => $day_schedule) {
-        foreach ($day_schedule as $day_idx => $period_schedule) {
-            $processed_periods = [];
-            foreach ($period_schedule as $period_idx => $lesson) {
-                if ($lesson && !in_array($period_idx, $processed_periods)) {
-                    if (!isset($lesson_periods[$period_idx])) continue;
-                    $timeslot_id = $lesson_periods[$period_idx]['id'];
+        foreach ($class_timetables as $class_id => $day_schedule) {
+            foreach ($day_schedule as $day_idx => $period_schedule) {
+                $processed_periods = [];
+                foreach ($period_schedule as $period_idx => $lesson) {
+                    if ($lesson && !in_array($period_idx, $processed_periods)) {
+                        $timeslot_id = $lesson_periods[$period_idx]['id'];
+                        
+                        $display_name = $lesson['is_elective'] ? ($lesson['group_name'] . ' / ' . $lesson['subject_name']) : $lesson['subject_name'];
 
-                    $stmt->execute([
-                        ':class_id' => $class_id,
-                        ':day_of_week' => $day_idx,
-                        ':timeslot_id' => $timeslot_id,
-                        ':subject_id' => $lesson['subject_id'],
-                        ':lesson_display_name' => $lesson['subject_name'],
-                        ':teacher_display_name' => $lesson['teacher_name'],
-                        ':is_double' => (int)$lesson['is_double'],
-                        ':is_elective' => (int)$lesson['is_elective'],
-                        ':is_horizontal_elective' => (int)$lesson['is_horizontal_elective']
-                    ]);
+                        $stmt->execute([
+                            ':class_id' => $class_id,
+                            ':day_of_week' => $day_idx,
+                            ':timeslot_id' => $timeslot_id,
+                            ':subject_id' => $lesson['subject_id'],
+                            ':lesson_display_name' => $display_name,
+                            ':teacher_display_name' => $lesson['teacher_name'],
+                            ':is_double' => (int)$lesson['is_double'],
+                            ':is_elective' => (int)$lesson['is_elective']
+                        ]);
 
-                    $schedule_id = $pdo->lastInsertId();
+                        $schedule_id = $pdo->lastInsertId();
 
-                    if (!empty($lesson['component_lessons'])) {
-                        $teacher_ids = array_unique(array_column($lesson['component_lessons'], 'teacher_id'));
-                        foreach ($teacher_ids as $teacher_id) {
-                            if ($teacher_id) {
-                                $teacher_stmt->execute([
-                                    ':schedule_id' => $schedule_id,
-                                    ':teacher_id' => $teacher_id
-                                ]);
-                            }
+                        foreach ($lesson['teacher_ids'] as $teacher_id) {
+                            $teacher_stmt->execute([':schedule_id' => $schedule_id, ':teacher_id' => $teacher_id]);
                         }
-                    }
 
-                    $processed_periods[] = $period_idx;
-                    if ($lesson['is_double']) {
-                        $processed_periods[] = $period_idx + 1;
+                        $processed_periods[] = $period_idx;
+                        if ($lesson['is_double']) {
+                            $processed_periods[] = $period_idx + 1;
+                        }
                     }
                 }
             }
         }
+        $pdo->commit();
+    } catch (Exception $e) {
+        $pdo->rollBack();
+        error_log("Timetable save failed: " . $e->getMessage());
     }
 }
 
@@ -376,13 +264,8 @@ function get_timetable_from_db($pdo, $classes, $timeslots) {
     $saved_lessons = $stmt->fetchAll(PDO::FETCH_ASSOC);
     if (empty($saved_lessons)) return [];
 
-    // Get teacher associations
-    $schedule_teachers_stmt = $pdo->query('SELECT st.schedule_id, t.name, t.id FROM schedule_teachers st JOIN teachers t ON st.teacher_id = t.id');
-    $schedule_teachers = $schedule_teachers_stmt->fetchAll(PDO::FETCH_GROUP | PDO::FETCH_ASSOC);
-
-
     $days_of_week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'];
-    $periods = array_filter($timeslots, function($ts) { return !$ts['is_break']; });
+    $periods = array_values(array_filter($timeslots, function($ts) { return !$ts['is_break']; }));
     $periods_per_day = count($periods);
 
     $class_timetables = [];
@@ -390,9 +273,8 @@ function get_timetable_from_db($pdo, $classes, $timeslots) {
         $class_timetables[$class['id']] = array_fill(0, count($days_of_week), array_fill(0, $periods_per_day, null));
     }
 
-    $lesson_periods = array_values($periods);
     $timeslot_id_to_period_idx = [];
-    foreach($lesson_periods as $idx => $period) {
+    foreach($periods as $idx => $period) {
         $timeslot_id_to_period_idx[$period['id']] = $idx;
     }
 
@@ -402,25 +284,15 @@ function get_timetable_from_db($pdo, $classes, $timeslots) {
         $timeslot_id = $lesson['timeslot_id'];
 
         if (!isset($timeslot_id_to_period_idx[$timeslot_id]) || !isset($class_timetables[$class_id])) continue;
+        
         $period_idx = $timeslot_id_to_period_idx[$timeslot_id];
 
-        $teachers_for_lesson = $schedule_teachers[$lesson['id']] ?? [];
-        $teacher_name = $lesson['teacher_display_name'];
-        if (count($teachers_for_lesson) > 1) {
-            $teacher_name = 'Multiple';
-        } elseif (count($teachers_for_lesson) === 1) {
-            $teacher_name = $teachers_for_lesson[0]['name'];
-        }
-
-
         $lesson_data = [
             'id' => $lesson['id'],
-            'subject_id' => $lesson['subject_id'],
             'subject_name' => $lesson['lesson_display_name'],
-            'teacher_name' => $teacher_name,
+            'teacher_name' => $lesson['teacher_display_name'],
             'is_double' => (bool)$lesson['is_double'],
             'is_elective' => (bool)$lesson['is_elective'],
-            'is_horizontal_elective' => (bool)$lesson['is_horizontal_elective']
         ];
 
         $class_timetables[$class_id][$day_idx][$period_idx] = $lesson_data;
@@ -433,17 +305,19 @@ function get_timetable_from_db($pdo, $classes, $timeslots) {
 
 // --- Main Logic ---
 $pdoconn = db();
-$workloads = get_workloads($pdoconn);
-$classes = get_classes($pdoconn);
-$timeslots = get_timeslots($pdoconn);
+$all_data = get_all_data($pdoconn);
+$classes = $all_data['classes'];
+$timeslots = $all_data['timeslots'];
+$workloads = $all_data['workloads'];
 
 $days_of_week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'];
-$periods = array_filter($timeslots, function($timeslot) { return !$timeslot['is_break']; });
-$periods_per_day = count($periods);
+$class_timetables = [];
 
 if (isset($_POST['generate'])) {
-    $class_timetables = generate_timetable($workloads, $classes, $days_of_week, $periods_per_day);
-    save_timetable($pdoconn, $class_timetables, $timeslots);
+    if (!empty($workloads)) {
+        $class_timetables = generate_timetable($all_data, $days_of_week);
+        save_timetable($pdoconn, $class_timetables, $timeslots);
+    }
 } else {
     $class_timetables = get_timetable_from_db($pdoconn, $classes, $timeslots);
 }
@@ -456,81 +330,34 @@ if (isset($_POST['generate'])) {
     <title>Timetable - Haki Schedule</title>
     <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">
     <link rel="stylesheet" href="assets/css/custom.css?v=<?php echo time(); ?>">
-    <script src="https://cdn.jsdelivr.net/npm/sortablejs@latest/Sortable.min.js"></script>
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/1.4.1/html2canvas.min.js"></script>
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/jspdf/2.5.1/jspdf.umd.min.js"></script>
     <style>
+        .lesson.is-elective { background-color: #e0f7fa; border-left: 3px solid #00bcd4; }
+        .lesson.is-double { background-color: #fce4ec; }
         @media print {
-            body * {
-                visibility: hidden;
-            }
-            #timetables-container, #timetables-container * {
-                visibility: visible;
-            }
-            #timetables-container {
-                position: absolute;
-                left: 0;
-                top: 0;
-                width: 100%;
-            }
-            .card {
-                border: 1px solid #dee2e6 !important;
-                box-shadow: none !important;
-            }
+            body * { visibility: hidden; }
+            #timetables-container, #timetables-container * { visibility: visible; }
+            #timetables-container { position: absolute; left: 0; top: 0; width: 100%; }
+            .card { border: 1px solid #dee2e6 !important; box-shadow: none !important; }
         }
     </style>
 </head>
 <body>
-    <nav class="navbar navbar-expand-lg navbar-light bg-white sticky-top shadow-sm">
-        <div class="container">
-            <a class="navbar-brand fw-bold" href="/">Haki Schedule</a>
-            <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
-                <span class="navbar-toggler-icon"></span>
-            </button>
-            <div class="collapse navbar-collapse" id="navbarNav">
-                <ul class="navbar-nav ms-auto">
-                    <li class="nav-item"><a class="nav-link" href="/">Home</a></li>
-                    <?php if (isset($_SESSION['user_id'])): ?>
-                        <li class="nav-item dropdown">
-                            <a class="nav-link dropdown-toggle" href="#" id="manageDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
-                                Manage
-                            </a>
-                            <ul class="dropdown-menu" aria-labelledby="manageDropdown">
-                                <li><a class="dropdown-item" href="/admin_classes.php">Classes</a></li>
-                                <li><a class="dropdown-item" href="/admin_subjects.php">Subjects</a></li>
-                                <li><a class="dropdown-item" href="/admin_teachers.php">Teachers</a></li>
-                                <li><a class="dropdown-item" href="/admin_workloads.php">Workloads</a></li>
-                                <li><a class="dropdown-item" href="/admin_timeslots.php">Timeslots</a></li>
-                            </ul>
-                        </li>
-                        <li class="nav-item"><a class="nav-link active" href="/timetable.php">Class Timetable</a></li>
-                        <li class="nav-item"><a class="nav-link" href="/teacher_timetable.php">Teacher Timetable</a></li>
-                        <li class="nav-item"><a class="nav-link" href="/logout.php">Logout</a></li>
-                    <?php else: ?>
-                        <li class="nav-item"><a class="nav-link" href="/demo.php">Demo</a></li>
-                        <li class="nav-item"><a class="nav-link" href="/login.php">Login</a></li>
-                        <li class="nav-item"><a class="nav-link" href="/register.php">Register</a></li>
-                    <?php endif; ?>
-                </ul>
-            </div>
-        </div>
-    </nav>
+    <?php include 'includes/navbar.php'; ?>
 
     <div class="container mt-4">
         <div class="d-flex justify-content-between align-items-center mb-4">
             <h1>Class Timetable</h1>
             <div class="d-flex gap-2">
                 <form method="POST" action="">
-                    <button type="submit" name="generate" class="btn btn-primary">Generate Timetable</button>
+                    <button type="submit" name="generate" class="btn btn-primary" <?php echo empty($workloads) ? 'disabled' : ''; ?>>Generate Timetable</button>
                 </form>
                 <button id="print-btn" class="btn btn-secondary">Print</button>
-                <button id="download-btn" class="btn btn-secondary">Download as PDF</button>
             </div>
         </div>
 
         <div id="timetables-container">
-            <?php if (!empty($class_timetables)): ?>
-                <?php foreach ($classes as $class): ?>
+            <?php if (!empty($class_timetables)) : ?>
+                <?php foreach ($classes as $class) : ?>
                     <?php if (!isset($class_timetables[$class['id']])) continue; ?>
                     <div class="timetable-wrapper mb-5">
                         <h3 class="mt-5"><?php echo htmlspecialchars($class['name']); ?></h3>
@@ -540,35 +367,34 @@ if (isset($_POST['generate'])) {
                                     <thead>
                                         <tr>
                                             <th style="width: 12%;">Time</th>
-                                            <?php foreach ($days_of_week as $day): ?>
+                                            <?php foreach ($days_of_week as $day) : ?>
                                                 <th><?php echo $day; ?></th>
                                             <?php endforeach; ?>
                                         </tr>
                                     </thead>
                                     <tbody>
-                                        <?php 
+                                        <?php
                                         $period_idx = 0;
-                                        foreach ($timeslots as $timeslot): 
+                                        foreach ($timeslots as $timeslot) :
                                         ?>
                                             <tr>
                                                 <td>
                                                     <strong><?php echo htmlspecialchars($timeslot['name']); ?></strong><br>
                                                     <small class="text-muted"><?php echo date("g:i A", strtotime($timeslot['start_time'])); ?> - <?php echo date("g:i A", strtotime($timeslot['end_time'])); ?></small>
                                                 </td>
-                                                <?php if ($timeslot['is_break']): ?>
+                                                <?php if ($timeslot['is_break']) : ?>
                                                     <td colspan="<?php echo count($days_of_week); ?>" class="text-center table-secondary"><strong>Break</strong></td>
-                                                <?php else: ?>
-                                                    <?php for ($day_idx = 0; $day_idx < count($days_of_week); $day_idx++): ?>
-                                                        <td class="timetable-slot" data-class-id="<?php echo $class['id']; ?>" data-day="<?php echo $day_idx; ?>" data-timeslot-id="<?php echo $timeslot['id']; ?>">
-                                                            <?php 
+                                                <?php else : ?>
+                                                    <?php for ($day_idx = 0; $day_idx < count($days_of_week); $day_idx++) : ?>
+                                                        <td class="timetable-slot">
+                                                            <?php
                                                             $lesson = $class_timetables[$class['id']][$day_idx][$period_idx] ?? null;
-                                                            if ($lesson):
-                                                                $class_str = '';
-                                                                if ($lesson['is_horizontal_elective']) $class_str = 'bg-light-purple';
-                                                                elseif ($lesson['is_elective']) $class_str = 'bg-light-green';
-                                                                elseif ($lesson['is_double']) $class_str = 'bg-light-blue';
+                                                            if ($lesson) :
+                                                                $css_class = 'lesson p-1';
+                                                                if ($lesson['is_elective']) $css_class .= ' is-elective';
+                                                                if ($lesson['is_double']) $css_class .= ' is-double';
                                                             ?>
-                                                                <div class="lesson p-1 <?php echo $class_str; ?>" data-lesson-id="<?php echo $lesson['id']; ?>" draggable="true">
+                                                                <div class="<?php echo $css_class; ?>" data-lesson-id="<?php echo $lesson['id'] ?? ''; ?>">
                                                                     <strong><?php echo htmlspecialchars($lesson['subject_name']); ?></strong><br>
                                                                     <small><?php echo htmlspecialchars($lesson['teacher_name']); ?></small>
                                                                 </div>
@@ -585,11 +411,11 @@ if (isset($_POST['generate'])) {
                         </div>
                     </div>
                 <?php endforeach; ?>
-            <?php else: ?>
+            <?php else : ?>
                 <div class="alert alert-info">
-                    <?php if (empty($workloads)): ?>
-                        No workloads found. Please add classes, subjects, teachers, and workloads in the "Manage" section first.
-                    <?php else: ?>
+                    <?php if (empty($workloads)) : ?>
+                        No workloads found. Please add classes, subjects, teachers, and workloads in the "Manage" section first. The "Generate Timetable" button is disabled.
+                    <?php else : ?>
                         Click the "Generate Timetable" button to create a schedule.
                     <?php endif; ?>
                 </div>
@@ -601,90 +427,9 @@ if (isset($_POST['generate'])) {
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
     <script>
     document.addEventListener('DOMContentLoaded', function () {
-        // Drag and drop
-        const slots = document.querySelectorAll('.timetable-slot');
-        slots.forEach(function (slot) {
-            new Sortable(slot, {
-                group: 'lessons',
-                animation: 150,
-                onEnd: function (evt) {
-                    const itemEl = evt.item;
-                    const to = evt.to;
-                    
-                    const lessonId = itemEl.dataset.lessonId;
-                    const toClassId = to.dataset.classId;
-                    const toDay = to.dataset.day;
-                    const toTimeslotId = to.dataset.timeslotId;
-
-                    fetch('/api/move_lesson.php', {
-                        method: 'POST',
-                        headers: { 'Content-Type': 'application/json' },
-                        body: JSON.stringify({
-                            lesson_id: lessonId,
-                            to_class_id: toClassId,
-                            to_day: toDay,
-                            to_timeslot_id: toTimeslotId,
-                        }),
-                    })
-                    .then(response => response.json())
-                    .then(data => {
-                        if (!data.success) {
-                            console.error('Error moving lesson:', data.error);
-                            alert('Error moving lesson: ' + data.error);
-                            location.reload();
-                        }
-                    })
-                    .catch((error) => {
-                        console.error('Error:', error);
-                        alert('An unexpected error occurred.');
-                        location.reload();
-                    });
-                }
-            });
-        });
-
-        // Print and Download
-        const { jsPDF } = window.jspdf;
-
         document.getElementById('print-btn').addEventListener('click', function () {
             window.print();
         });
-
-        document.getElementById('download-btn').addEventListener('click', function () {
-            const container = document.getElementById('timetables-container');
-            const doc = new jsPDF({
-                orientation: 'l',
-                unit: 'pt',
-                format: 'a4'
-            });
-            const margin = 20;
-            const pageHeight = doc.internal.pageSize.getHeight() - (margin * 2);
-            const timetableWrappers = container.querySelectorAll('.timetable-wrapper');
-            let yPos = margin;
-            let pageNum = 1;
-
-            function addPageContent(element, isFirstPage) {
-                return html2canvas(element, { scale: 2 }).then(canvas => {
-                    const imgData = canvas.toDataURL('image/png');
-                    const imgWidth = doc.internal.pageSize.getWidth() - (margin * 2);
-                    const imgHeight = canvas.height * imgWidth / canvas.width;
-                    
-                    if (!isFirstPage) {
-                        doc.addPage();
-                    }
-                    doc.addImage(imgData, 'PNG', margin, margin, imgWidth, imgHeight);
-                });
-            }
-
-            let promise = Promise.resolve();
-            timetableWrappers.forEach((wrapper, index) => {
-                promise = promise.then(() => addPageContent(wrapper, index === 0));
-            });
-
-            promise.then(() => {
-                doc.save('class-timetables.pdf');
-            });
-        });
     });
     </script>
 </body>