:root {
    --primary-color: #FF4081;
    --primary-dark: #C51162;
    --sidebar-bg: #1A1A2E;
    --sidebar-hover: #262642;
    --bg-color: #F8F9FA;
    --text-color: #333333;
    --text-muted: #666666;
    --white: #FFFFFF;
    --border-radius: 12px;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    height: 100vh;
    overflow: hidden;
    /* App-like feel */
}

/* Layout */
.app-container {
    display: flex;
    height: 100%;
}

/* Sidebar */
.sidebar {
    width: 280px;
    background-color: var(--sidebar-bg);
    color: var(--white);
    display: flex;
    flex-direction: column;
    transition: transform 0.3s ease;
    flex-shrink: 0;
    overflow-y: auto;
}

.brand {
    padding: 24px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.close-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--white);
    font-size: 24px;
    cursor: pointer;
    font-weight: bold;
}

.brand h1 {
    font-size: 24px;
    font-weight: 700;
}

.brand span {
    color: var(--primary-color);
}

.modules-nav {
    padding: 20px 0;
}

.module-header {
    padding: 10px 24px;
    font-size: 14px;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: rgba(255, 255, 255, 0.5);
    margin-top: 15px;
    font-weight: 600;
}

.lesson-link {
    display: flex;
    align-items: center;
    padding: 12px 24px;
    cursor: pointer;
    transition: background 0.2s;
    font-size: 16px;
    color: rgba(255, 255, 255, 0.9);
}

.lesson-link:hover {
    background-color: var(--sidebar-hover);
}

.lesson-link.active {
    background-color: var(--primary-color);
    color: var(--white);
    font-weight: 600;
}

.lesson-icon {
    margin-right: 12px;
    font-size: 18px;
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    position: relative;
}

.top-bar {
    height: 70px;
    background-color: var(--white);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 30px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.03);
}

.menu-btn {
    display: none;
    /* Show on mobile */
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--text-color);
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 600;
}

.avatar {
    width: 40px;
    height: 40px;
    background-color: var(--primary-color);
    color: var(--white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
}

.content-wrapper {
    flex: 1;
    overflow-y: auto;
    padding: 40px;
}

.lesson-container {
    max-width: 900px;
    margin: 0 auto;
    background-color: var(--white);
    padding: 40px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.lesson-title {
    font-size: 32px;
    margin-bottom: 24px;
    color: var(--text-color);
}

.video-placeholder {
    width: 100%;
    height: 400px;
    background-color: #222;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 30px;
}

.play-icon {
    font-size: 60px;
    color: white;
    opacity: 0.8;
}

.lesson-body {
    font-size: 18px;
    /* High accessibility */
    line-height: 1.8;
    color: var(--text-color);
}

.lesson-body p {
    margin-bottom: 20px;
}

.lesson-body img {
    max-width: 100%;
    border-radius: 12px;
    margin: 20px 0;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.lesson-body h3 {
    font-size: 24px;
    margin-top: 30px;
    margin-bottom: 15px;
    color: var(--primary-color);
}

.highlight-box {
    background-color: #FFF0F5;
    /* Light Pink */
    border-left: 5px solid var(--primary-color);
    padding: 20px;
    border-radius: 8px;
    margin: 24px 0;
}

.navigation-controls {
    display: flex;
    justify-content: space-between;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid #eee;
}

.nav-btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    background-color: var(--primary-color);
    color: var(--white);
    transition: transform 0.2s;
}

.nav-btn:disabled {
    background-color: #ddd;
    cursor: not-allowed;
}

.nav-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    background-color: var(--primary-dark);
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        left: -280px;
        height: 100%;
        z-index: 1000;
    }

    .sidebar.active {
        transform: translateX(280px);
    }

    .menu-btn {
        display: block;
    }

    .close-menu-btn {
        display: block;
    }

    .content-wrapper {
        padding: 20px;
        padding-bottom: 100px;
    }

    .lesson-container {
        padding: 25px;
        margin-bottom: 40px;
    }

    .lesson-title {
        font-size: 24px;
    }
}