body {
    background-color: #f8f9fa;
    min-height: 100vh;
}

.card {
    border: none;
    border-radius: 10px;
}

.card-header {
    border-radius: 10px 10px 0 0 !important;
}

.hover-shadow:hover {
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.15) !important;
    transform: translateY(-2px);
}

.lesson-content {
    font-size: 1.1rem;
    line-height: 1.8;
}

.lesson-content p {
    margin-bottom: 1.5rem;
}

.lesson-content h3 {
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: #0d6efd;
}

.lesson-content ul, .lesson-content ol {
    margin-bottom: 1.5rem;
}

.lesson-content li {
    margin-bottom: 0.5rem;
}

/* ========================================
   RESPONSIVE IMAGES & VIDEOS SYSTEM
   ======================================== */

/* Default Image Styling - Mobile First */
.lesson-content img {
    max-width: 100%;
    height: auto !important;
    display: block;
    margin: 1.5rem auto;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.lesson-content img:hover {
    transform: scale(1.02);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.2);
}

/* Image Layout Classes */

/* Full Width Image */
.lesson-content .img-full {
    width: 100%;
    max-width: 100%;
    margin: 2rem 0;
}

/* Center Image (default behavior on mobile) */
.lesson-content .img-center {
    display: block;
    margin: 1.5rem auto;
    max-width: 100%;
}

/* Left Float Image - Desktop only, stacks on mobile */
.lesson-content .img-left {
    display: block;
    margin: 1.5rem auto;
    max-width: 100%;
}

/* Right Float Image - Desktop only, stacks on mobile */
.lesson-content .img-right {
    display: block;
    margin: 1.5rem auto;
    max-width: 100%;
}

/* Small Image (thumbnail size) */
.lesson-content .img-small {
    max-width: 300px;
    margin: 1rem auto;
}

/* Medium Image */
.lesson-content .img-medium {
    max-width: 500px;
    margin: 1.5rem auto;
}

/* Large Image */
.lesson-content .img-large {
    max-width: 800px;
    margin: 2rem auto;
}

/* Desktop & Tablet Responsive Behavior */
@media (min-width: 768px) {
    /* Left Float on Desktop */
    .lesson-content .img-left {
        float: left;
        margin: 0.5rem 1.5rem 1rem 0;
        max-width: 45%;
        display: inline-block;
    }
    
    /* Right Float on Desktop */
    .lesson-content .img-right {
        float: right;
        margin: 0.5rem 0 1rem 1.5rem;
        max-width: 45%;
        display: inline-block;
    }
    
    /* Clear floats after images */
    .lesson-content .img-left + p,
    .lesson-content .img-right + p {
        display: inline;
    }
}

/* Mobile Override - Stack All Images */
@media (max-width: 767px) {
    .lesson-content img,
    .lesson-content .img-left,
    .lesson-content .img-right,
    .lesson-content .img-center {
        float: none !important;
        display: block !important;
        margin: 1.5rem auto !important;
        max-width: 100% !important;
        width: 100% !important;
    }
}

/* Image Caption Styling */
.lesson-content .img-caption {
    text-align: center;
    font-style: italic;
    color: #6c757d;
    font-size: 0.9rem;
    margin-top: 0.5rem;
    margin-bottom: 1.5rem;
}

/* Image Container with Caption */
.lesson-content .img-container {
    margin: 1.5rem 0;
    display: inline-block;
    max-width: 100%;
}

.lesson-content .img-container.left {
    float: left;
    margin-right: 1.5rem;
    max-width: 45%;
}

.lesson-content .img-container.right {
    float: right;
    margin-left: 1.5rem;
    max-width: 45%;
}

@media (max-width: 767px) {
    .lesson-content .img-container,
    .lesson-content .img-container.left,
    .lesson-content .img-container.right {
        float: none !important;
        display: block !important;
        margin: 1.5rem auto !important;
        max-width: 100% !important;
        width: 100% !important;
    }
}

/* ========================================
   VIDEO EMBEDS
   ======================================== */

/* Responsive Video Container */
.lesson-content .video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
    overflow: hidden;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    margin: 2rem 0;
    background: #000;
}

.lesson-content .video-container iframe,
.lesson-content .video-container video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
    border-radius: 12px;
}

/* Video Caption */
.lesson-content .video-caption {
    text-align: center;
    font-style: italic;
    color: #6c757d;
    font-size: 0.9rem;
    margin-top: 0.5rem;
    margin-bottom: 1.5rem;
}

/* Alternative square video (1:1) */
.lesson-content .video-container.square {
    padding-bottom: 100%;
}

/* Alternative vertical video (9:16) */
.lesson-content .video-container.vertical {
    padding-bottom: 177.78%;
    max-width: 400px;
    margin-left: auto;
    margin-right: auto;
}

/* Clear floats helper */
.lesson-content .clearfix::after {
    content: "";
    display: table;
    clear: both;
}

#nextButton:disabled {
    cursor: not-allowed;
    opacity: 0.6;
}

.progress {
    border-radius: 10px;
}

.navbar-brand {
    font-weight: bold;
    font-size: 1.5rem;
}

.modal-content {
    border-radius: 15px;
}

.modal-header {
    border-radius: 15px 15px 0 0;
}

.form-control:focus {
    border-color: #0d6efd;
    box-shadow: 0 0 0 0.25rem rgba(13, 110, 253, 0.25);
}

.alert {
    border-radius: 10px;
}

.btn {
    border-radius: 8px;
}

.shadow {
    box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.15) !important;
}