:root {
    --primary: #1976D2;
    --primary-dark: #115293;
    --secondary: #2E7D32;
    --secondary-light: #4caf50;
    --background: #F5F5F5;
    --surface: #FFFFFF;
    --text-primary: #000000;
    --text-secondary: #555555;
    --error: #D32F2F;
}

body {
    font-family: 'Inter', 'Roboto', sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    color: var(--primary);
    margin-top: 0;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.2s ease;
}

a:hover {
    color: var(--primary-dark);
}

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

header {
    background-color: var(--surface);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.brand {
    font-family: 'Georgia', serif;
    font-weight: 700;
    font-size: 1.5rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    align-items: center;
}

/* Cards */
.card {
    background-color: var(--surface);
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    padding: 1.5rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    margin-bottom: 1.5rem;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    border: none;
    transition: all 0.3s ease;
    text-align: center;
}

.btn-primary {
    background-color: var(--primary);
    color: white;
}

.btn-primary:hover {
    background-color: var(--primary-dark);
    color: white;
    transform: scale(1.05);
}

.btn-success {
    background-color: var(--secondary);
    color: white;
}

.btn-success:hover {
    background-color: var(--secondary-light);
    color: white;
    transform: scale(1.05);
}

.btn-danger {
    background-color: var(--error);
    color: white;
}

.btn-outline {
    background-color: transparent;
    border: 2px solid var(--primary);
    color: var(--primary);
}

.btn-outline:hover {
    background-color: var(--primary);
    color: white;
}

/* Forms */
.form-group {
    margin-bottom: 1.5rem;
}

.form-control {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
    box-sizing: border-box;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(25, 118, 210, 0.2);
}

/* Alerts */
.alert {
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
}

.alert-error {
    background-color: #ffebee;
    color: var(--error);
    border: 1px solid #ffcdd2;
}

.alert-success {
    background-color: #e8f5e9;
    color: var(--secondary);
    border: 1px solid #c8e6c9;
}

/* Progress */
.progress-bar-container {
    width: 100%;
    height: 8px;
    background-color: #e0e0e0;
    border-radius: 4px;
    overflow: hidden;
    margin-top: 0.5rem;
}

.progress-bar {
    height: 100%;
    background-color: var(--secondary);
    transition: width 0.5s ease-in-out;
}

/* Lesson specific */
.lesson-list {
    list-style: none;
    padding: 0;
}

.lesson-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    border-bottom: 1px solid #eee;
    transition: background-color 0.2s;
}

.lesson-item:hover {
    background-color: #f9f9f9;
}

.lesson-item.completed .lesson-title {
    color: var(--secondary);
}

/* Audio Player */
.audio-player-container {
    background: var(--surface);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.1);
    text-align: center;
    margin: 2rem auto;
    max-width: 600px;
}

audio {
    width: 100%;
    margin-top: 1rem;
    outline: none;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.animate-fade-in {
    animation: fadeIn 0.5s ease forwards;
}

/* Utilities */
.text-center { text-align: center; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.d-flex { display: flex; }
.justify-between { justify-content: space-between; }
.align-center { align-items: center; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }