:root {
    --primary-color: #1a237e;
    --secondary-color: #ffab40;
    --accent-color: #448aff;
    --background-color: #f5f5f5;
    --text-color: #212121;
    --heading-font: 'Poppins', sans-serif;
    --body-font: 'Roboto', sans-serif;
}

body {
    font-family: var(--body-font);
    background-color: var(--background-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--heading-font);
    color: var(--primary-color);
}

.navbar {
    background-color: #ffffff;
    border-bottom: 1px solid #e0e0e0;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.navbar-brand {
    font-family: var(--heading-font);
    font-weight: 600;
    font-size: 1.5rem;
    color: var(--primary-color);
    text-decoration: none;
}

.hero {
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: #ffffff;
    padding: 4rem 2rem;
    text-align: center;
    border-bottom-left-radius: 30px;
    border-bottom-right-radius: 30px;
}

.hero h1 {
    color: #ffffff;
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.container {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 2rem;
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

.problem-card {
    background-color: #ffffff;
    border-radius: 15px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    padding: 1.5rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.problem-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 12px rgba(0,0,0,0.15);
}

.problem-card h3 {
    margin-top: 0;
    font-size: 1.25rem;
}

.problem-meta {
    font-size: 0.9rem;
    color: #757575;
}

.problem-meta span {
    margin-right: 1rem;
}

.level-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
    text-transform: capitalize;
}

.level-easy {
    background-color: #e8f5e9;
    color: #4caf50;
}

.level-medium {
    background-color: #fff3e0;
    color: #ff9800;
}

.level-hard {
    background-color: #ffebee;
    color: #f44336;
}