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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
    padding: 10px;
}

.container {
    max-width: 100%;
    margin: 0 auto;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 20px;
}

.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid #e0e0e0;
    flex-wrap: wrap;
}

.page-header h1 {
    font-size: 1.5rem;
    color: #232D4B;
    flex: 1;
    min-width: 200px;
}

.back-link {
    color: #E57200;
    text-decoration: none;
    font-size: 0.95rem;
    padding: 8px 12px;
    border: 1px solid #E57200;
    border-radius: 4px;
    transition: background-color 0.2s;
}

.back-link:hover {
    background-color: #E57200;
    color: white;
}

.intro {
    text-align: center;
    margin-bottom: 30px;
    font-size: 1rem;
    color: #555;
    padding: 0 10px;
}

.navigation {
    margin-top: 20px;
}

.exercise-nav {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.exercise-link {
    display: block;
    padding: 20px;
    background-color: #f8f9fa;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    text-decoration: none;
    color: #333;
    transition: all 0.2s;
    min-height: 80px;
}

.exercise-link:hover {
    background-color: #E57200;
    color: white;
    border-color: #E57200;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

.exercise-link h4 {
    font-size: 1.2rem;
    margin-bottom: 8px;
    color: inherit;
}

.exercise-link p {
    font-size: 0.95rem;
    color: inherit;
    opacity: 0.9;
}

.exercise-container {
    width: 100%;
}

.info-box,
.teaching-box,
.warning-box {
    padding: 14px 16px;
    margin-bottom: 15px;
    border-radius: 4px;
}

.info-box {
    background-color: #e3f2fd;
    border-left: 4px solid #2196F3;
}

.teaching-box {
    background-color: #f8f9fa;
    border-left: 4px solid #232D4B;
}

.warning-box {
    background-color: #fff3e0;
    border-left: 4px solid #E57200;
}

.info-box p,
.teaching-box p,
.warning-box p {
    margin: 0 0 8px;
}

.info-box p:last-child,
.teaching-box p:last-child,
.warning-box p:last-child {
    margin-bottom: 0;
}

.vignette-card {
    background: #f8f9fa;
    border: 1px solid #ddd;
    border-radius: 8px;
    padding: 18px;
    margin-bottom: 20px;
}

.vignette-card h2,
.section-heading {
    color: #232D4B;
    margin-bottom: 10px;
}

.section-heading {
    margin-top: 10px;
}

.buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 20px;
    justify-content: center;
}

.btn {
    padding: 12px 24px;
    font-size: 1rem;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.2s;
    min-height: 44px;
    min-width: 120px;
    flex: 1;
    max-width: 220px;
}

.btn-primary {
    background-color: #E57200;
    color: white;
}

.btn-primary:hover {
    background-color: #d16500;
    transform: translateY(-1px);
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
}

.btn-secondary {
    background-color: #6c757d;
    color: white;
}

.btn-secondary:hover {
    background-color: #5a6268;
    transform: translateY(-1px);
}

.btn-blue {
    background-color: #2196F3;
    color: white;
}

.btn-blue:hover {
    background-color: #1976D2;
    transform: translateY(-1px);
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
}

.hidden {
    display: none;
}

.result-callout {
    border: 2px solid #E57200;
    border-radius: 8px;
    padding: 16px;
    margin: 15px 0;
    background: #fff8f0;
}

.result-callout h2 {
    color: #232D4B;
    margin-bottom: 8px;
}

/* Quiz */
.quiz-form {
    max-width: 700px;
    margin: 0 auto;
}

.question-block {
    background-color: #f8f9fa;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 20px;
}

.question-prompt {
    font-weight: 600;
    font-size: 1.05rem;
    margin-bottom: 14px;
    color: #232D4B;
}

.previous-answer {
    font-size: 0.85rem;
    color: #888;
    font-style: italic;
    margin-bottom: 10px;
    padding: 6px 10px;
    background-color: #f0f0f0;
    border-radius: 4px;
}

.options-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.option-label {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    padding: 10px 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.15s;
}

.option-label:hover {
    background-color: #e8e8e8;
}

.option-label input[type="radio"] {
    margin-top: 4px;
    accent-color: #E57200;
}

.option-label.correct-option {
    background-color: #e8f5e9;
    border: 1px solid #66bb6a;
}

.option-label.incorrect-option {
    background-color: #fce4ec;
    border: 1px solid #ef5350;
}

.feedback {
    margin-top: 12px;
    padding: 12px 14px;
    border-radius: 6px;
    font-size: 0.93rem;
    line-height: 1.5;
}

.feedback-correct {
    background-color: #e8f5e9;
    border-left: 4px solid #66bb6a;
    color: #2e7d32;
}

.feedback-incorrect {
    background-color: #fce4ec;
    border-left: 4px solid #ef5350;
    color: #c62828;
}

.quiz-error {
    color: #c62828;
    text-align: center;
    font-weight: 500;
    margin-top: 10px;
}

.hill-intro p {
    margin-bottom: 10px;
}

.hill-intro p:last-child {
    margin-bottom: 0;
}

/* Hill table */
.table-wrap {
    overflow-x: auto;
    margin: 20px 0;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
}

.hill-table-interactive {
    touch-action: auto;
}

.hill-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.92rem;
    table-layout: fixed;
}

.hill-table th:nth-child(1),
.hill-table td:nth-child(1) {
    width: 8%;
}

.hill-table th:nth-child(2),
.hill-table td:nth-child(2) {
    width: 22%;
}

.hill-table th:nth-child(3),
.hill-table td:nth-child(3) {
    width: 30%;
}

.hill-table th:nth-child(4),
.hill-table td:nth-child(4) {
    width: 40%;
}

.hill-table th,
.hill-table td {
    padding: 10px 12px;
    border-bottom: 1px solid #e0e0e0;
    text-align: left;
    vertical-align: top;
}

.hill-table th {
    background-color: #232D4B;
    color: white;
    font-weight: 600;
}

.hill-reveal-cell {
    padding: 8px 10px;
    vertical-align: top;
}

.hill-reveal-row {
    width: 100%;
}

.hill-reveal-stack {
    position: relative;
    min-height: 2.8em;
    padding: 8px 10px;
    border-radius: 6px;
    background: #fafbfc;
    border: 1px solid #e8ecf0;
}

.hill-reveal-text {
    display: block;
    line-height: 1.45;
    font-size: 0.9rem;
}

.hill-reveal-cover {
    position: absolute;
    inset: 0;
    border-radius: 6px;
    background: linear-gradient(90deg, #dfe6f3 0%, #cfd9ea 100%);
    border: 1px solid #b8c5dc;
    color: #5c6b88;
    font-size: 0.82rem;
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: opacity 0.2s ease, transform 0.15s ease;
}

.hill-reveal-cover:hover {
    background: linear-gradient(90deg, #d5ddea 0%, #c5d0e2 100%);
    color: #232D4B;
}

.hill-reveal-cover:active {
    transform: scale(0.99);
}

.hill-reveal-row.hill-revealed .hill-reveal-cover {
    opacity: 0;
    pointer-events: none;
}

.hill-table tbody tr:nth-child(even) .hill-reveal-stack {
    background: #f3f6fa;
}

.hill-table tbody tr:nth-child(even) .hill-reveal-cover {
    background: linear-gradient(90deg, #d5ddea 0%, #c5d0e2 100%);
}

.hill-table tbody tr:nth-child(even) {
    background-color: #f8f9fa;
}

.hill-table tbody tr:last-child td {
    border-bottom: none;
}

.table-note {
    font-size: 0.8rem;
    font-weight: 400;
    color: #666;
}

/* DAG drawing intro */
.dag-draw-section {
    margin-bottom: 28px;
}

.dag-draw-section > p {
    margin-bottom: 12px;
    color: #555;
}

.dag-draw-board {
    width: 100%;
    margin: 12px 0;
    background-color: white;
    border: 1px solid #ddd;
    border-radius: 8px;
    padding: 8px;
    touch-action: none;
    user-select: none;
}

.dag-draw-svg {
    width: 100%;
    height: auto;
    display: block;
    cursor: crosshair;
}

.dag-draw-node rect {
    fill: #f8f9fa;
    stroke: #232D4B;
    stroke-width: 2;
    transition: fill 0.15s ease, stroke 0.15s ease;
}

.dag-draw-node text {
    fill: #232D4B;
    font-size: 13px;
    font-weight: 600;
    font-family: inherit;
    pointer-events: none;
}

.dag-draw-node.active rect,
.dag-draw-node.hover-target rect {
    fill: #fff8f0;
    stroke: #E57200;
    stroke-width: 3;
}

.dag-draw-edge {
    stroke: #232D4B;
    stroke-width: 2.5;
}

.dag-draw-preview {
    stroke: #E57200;
    stroke-width: 2.5;
    stroke-dasharray: 6 4;
    pointer-events: none;
}

.dag-spurious-link {
    fill: none;
    stroke: #E57200;
    stroke-width: 2.5;
    stroke-dasharray: 8 6;
    pointer-events: none;
}

.dag-draw-feedback {
    padding: 14px 16px;
    margin-bottom: 12px;
    border-radius: 4px;
    font-size: 0.95rem;
    line-height: 1.55;
}

.dag-draw-feedback.feedback-info {
    background-color: #e3f2fd;
    border-left: 4px solid #2196F3;
}

.dag-draw-feedback.feedback-success {
    background-color: #e8f5e9;
    border-left: 4px solid #66bb6a;
}

.dag-draw-feedback.feedback-warning {
    background-color: #fff3e0;
    border-left: 4px solid #E57200;
}

.dag-action-row {
    margin-top: 8px;
    margin-bottom: 0;
}

.dag-action-row .btn {
    max-width: 280px;
}

@media (min-width: 768px) {
    body {
        padding: 20px;
    }

    .container {
        max-width: 900px;
        padding: 30px;
    }

    .page-header h1 {
        font-size: 1.8rem;
    }
}

@media print {
    body {
        background-color: white;
    }

    .buttons,
    .dag-action-row {
        display: none;
    }
}