@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+Sinhala:wght@300;400;500;600;700&display=swap');

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #1e3c72 0%, #2a5298 100%);
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    background: #ffffff;
    border-radius: 20px;
    padding: 40px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.back-btn {
    display: inline-block;
    padding: 10px 20px;
    background: #2a5298;
    color: white;
    text-decoration: none;
    border-radius: 8px;
    margin-bottom: 20px;
    transition: background 0.3s;
}

.back-btn:hover {
    background: #1e3c72;
}

h1 {
    color: #1e3c72;
    margin-bottom: 10px;
}

.lesson-number {
    color: #2a5298;
    font-size: 1.1rem;
    font-weight: bold;
}

.tabs {
    display: flex;
    gap: 10px;
    margin: 30px 0 20px 0;
    border-bottom: 2px solid #e0e0e0;
}

.tab {
    padding: 12px 24px;
    cursor: pointer;
    border: none;
    background: none;
    font-size: 1rem;
    color: #666;
    border-bottom: 3px solid transparent;
    transition: all 0.3s;
}

.tab.active {
    color: #2a5298;
    border-bottom-color: #2a5298;
    font-weight: bold;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.5s;
}

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

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

.concept-card {
    background: #f8f9fa;
    padding: 25px;
    border-radius: 12px;
    margin-bottom: 20px;
    border-left: 4px solid #2a5298;
}

.concept-card h3 {
    color: #1e3c72;
    margin-bottom: 15px;
}

.concept-card p {
    line-height: 1.8;
    color: #555;
    margin-bottom: 10px;
}

.example-box {
    background: #fff9e6;
    border-left: 4px solid #f39c12;
    padding: 15px;
    margin: 15px 0;
    border-radius: 8px;
}

.example-box strong {
    color: #d68910;
}

.sinhala-box {
    background: #e8f5e9;
    border-left: 4px solid #4caf50;
    padding: 20px;
    margin: 15px 0;
    border-radius: 8px;
    font-family: 'Noto Sans Sinhala', 'Segoe UI', sans-serif;
    font-size: 1.05rem;
    line-height: 1.9;
}

.sinhala-box h3 {
    color: #2e7d32;
    margin-bottom: 12px;
    font-family: 'Noto Sans Sinhala', 'Segoe UI', sans-serif;
}

.sinhala-box p,
.sinhala-box li,
.sinhala-box ul,
.sinhala-box ol {
    font-family: 'Noto Sans Sinhala', 'Segoe UI', sans-serif;
}

.highlight {
    background: #fff9c4;
    padding: 2px 6px;
    border-radius: 3px;
    font-weight: 600;
    color: #1e3c72;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
}

th,
td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

th {
    background: #2a5298;
    color: white;
}

tr:hover {
    background: #f5f8fa;
}

.complete-btn {
    display: block;
    width: 100%;
    padding: 15px;
    background: #4caf50;
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    cursor: pointer;
    margin-top: 30px;
    transition: background 0.3s;
}

.complete-btn:hover {
    background: #43a047;
}

.complete-btn.completed {
    background: #757575;
}

ul,
ol {
    margin-left: 20px;
    line-height: 1.8;
    color: #555;
}

li {
    margin-bottom: 8px;
}

code {
    background: #f4f4f4;
    padding: 2px 6px;
    border-radius: 3px;
    font-family: 'Courier New', monospace;
    color: #d63384;
}

pre {
    background: #f4f4f4;
    padding: 15px;
    border-radius: 5px;
    overflow-x: auto;
}

.vs-box {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 20px;
    margin: 20px 0;
    align-items: center;
}

.vs-item {
    background: #eceff1;
    padding: 20px;
    border-radius: 10px;
    border: 2px solid #b0bec5;
}

.vs-divider {
    font-size: 2rem;
    font-weight: bold;
    color: #2a5298;
}

.diagram-container {
    text-align: center;
    margin: 20px 0;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 8px;
}

.diagram-container img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.diagram-caption {
    margin-top: 10px;
    font-size: 0.9rem;
    color: #666;
    font-style: italic;
}