/* Applied Mathematics - Dark Mode Learning Book */
:root {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --accent-blue: #58a6ff;
    --accent-green: #3fb950;
    --accent-purple: #a371f7;
    --accent-orange: #d29922;
    --accent-red: #f85149;
    --accent-cyan: #39c5cf;
    --border-color: #30363d;
    --formula-bg: #1c2128;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.8;
    font-size: 1.25rem;
    padding: 2rem 4rem;
    max-width: 100%;
}

/* Index Page Styles */
.index-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
}

.index-title {
    font-size: 3.5rem;
    margin-bottom: 1rem;
    color: var(--accent-blue);
    text-align: center;
}

.index-subtitle {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
    text-align: center;
}

.modules-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    width: 100%;
    max-width: 1400px;
}

.module-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 2rem;
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.3s ease;
    display: flex;
    flex-direction: column;
}

.module-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-blue);
    box-shadow: 0 10px 40px rgba(88, 166, 255, 0.15);
}

.module-number {
    font-size: 3rem;
    font-weight: bold;
    color: var(--accent-purple);
    margin-bottom: 0.5rem;
}

.module-title {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--accent-blue);
}

.module-topics {
    font-size: 1rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Content Styles */
h1 {
    font-size: 3rem;
    color: var(--accent-blue);
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 3px solid var(--accent-purple);
}

h2 {
    font-size: 2.2rem;
    color: var(--accent-green);
    margin: 3rem 0 1.5rem 0;
    padding-left: 1rem;
    border-left: 5px solid var(--accent-green);
}

h3 {
    font-size: 1.8rem;
    color: var(--accent-orange);
    margin: 2rem 0 1rem 0;
}

h4 {
    font-size: 1.4rem;
    color: var(--accent-cyan);
    margin: 1.5rem 0 1rem 0;
}

p {
    margin-bottom: 1.2rem;
}

/* Formula Box */
.formula-box {
    background: var(--formula-bg);
    border: 2px solid var(--accent-purple);
    border-radius: 10px;
    padding: 1.5rem 2rem;
    margin: 1.5rem 0;
    font-size: 1.4rem;
    text-align: center;
    overflow-x: auto;
}

.formula-box.important {
    border-color: var(--accent-orange);
    background: linear-gradient(135deg, rgba(210, 153, 34, 0.1), rgba(28, 33, 40, 1));
}

/* Definition Box */
.definition {
    background: var(--bg-secondary);
    border-left: 5px solid var(--accent-blue);
    padding: 1.5rem 2rem;
    margin: 1.5rem 0;
    border-radius: 0 10px 10px 0;
}

.definition-title {
    color: var(--accent-blue);
    font-weight: bold;
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

/* Example Box */
.example {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 2rem;
    margin: 2rem 0;
}

.example-title {
    color: var(--accent-green);
    font-size: 1.4rem;
    font-weight: bold;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.example-title::before {
    content: "✎";
    font-size: 1.2rem;
}

/* Steps */
.steps {
    margin: 1rem 0;
    padding-left: 0;
    list-style: none;
    counter-reset: step-counter;
}

.steps li {
    counter-increment: step-counter;
    padding: 1rem 1rem 1rem 3.5rem;
    position: relative;
    margin-bottom: 0.5rem;
    background: var(--bg-secondary);
    border-radius: 8px;
}

.steps li::before {
    content: "Step " counter(step-counter);
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    background: var(--accent-purple);
    color: white;
    padding: 0.3rem 0.6rem;
    border-radius: 5px 0 0 5px;
    font-size: 0.9rem;
    font-weight: bold;
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
    font-size: 1.2rem;
}

th, td {
    border: 1px solid var(--border-color);
    padding: 1rem 1.5rem;
    text-align: center;
}

th {
    background: var(--accent-purple);
    color: white;
    font-weight: bold;
    font-size: 1.3rem;
}

tr:nth-child(even) {
    background: var(--bg-secondary);
}

tr:nth-child(odd) {
    background: var(--bg-tertiary);
}

/* Flow Diagram */
.flow {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin: 2rem 0;
    padding: 1.5rem;
    background: var(--bg-secondary);
    border-radius: 10px;
}

.flow-step {
    background: var(--accent-blue);
    color: var(--bg-primary);
    padding: 1rem 1.5rem;
    border-radius: 8px;
    font-weight: bold;
    font-size: 1.1rem;
}

.flow-arrow {
    font-size: 2rem;
    color: var(--accent-orange);
}

/* Condition Box */
.condition {
    background: linear-gradient(135deg, rgba(248, 81, 73, 0.1), var(--bg-secondary));
    border: 2px solid var(--accent-red);
    border-radius: 10px;
    padding: 1.5rem 2rem;
    margin: 1.5rem 0;
}

.condition-title {
    color: var(--accent-red);
    font-weight: bold;
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

/* Property Box */
.property {
    background: var(--bg-secondary);
    border: 1px solid var(--accent-cyan);
    border-radius: 10px;
    padding: 1.5rem 2rem;
    margin: 1.5rem 0;
}

.property-title {
    color: var(--accent-cyan);
    font-weight: bold;
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

/* Note Box */
.note {
    background: rgba(210, 153, 34, 0.1);
    border-left: 4px solid var(--accent-orange);
    padding: 1rem 1.5rem;
    margin: 1rem 0;
    border-radius: 0 8px 8px 0;
    font-style: italic;
}

/* Highlight */
.highlight {
    background: rgba(88, 166, 255, 0.2);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
}

/* Math Expression Styling */
.math {
    font-family: 'Cambria Math', 'Times New Roman', serif;
    font-size: 1.3em;
    color: var(--accent-cyan);
}

/* Section Divider */
.divider {
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--accent-purple), transparent);
    margin: 3rem 0;
}

/* Grid Layout for Formulas */
.formula-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.formula-card {
    background: var(--formula-bg);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 1.5rem;
    text-align: center;
}

.formula-card-title {
    color: var(--accent-orange);
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

/* Answer Highlight */
.answer {
    background: linear-gradient(135deg, rgba(63, 185, 80, 0.2), rgba(63, 185, 80, 0.05));
    border: 2px solid var(--accent-green);
    border-radius: 8px;
    padding: 1rem 1.5rem;
    margin: 1rem 0;
    font-weight: bold;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 5px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--accent-blue);
}

/* Responsive for large screens */
@media (min-width: 1600px) {
    body {
        padding: 2rem 8rem;
    }
}

/* Print Styles */
@media print {
    body {
        background: white;
        color: black;
    }
}