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

html {
    overflow-x: auto;
    width: 100%;
    min-width: 0;
}

:root {
    --primary-color: #5865f2;
    --secondary-color: #7289da;
    --accent-color: #e74c3c;
    --success-color: #27ae60;
    --error-color: #e74c3c;
    --nested-highlight: #d946ef;
    --module1-color: #60a5fa;
    --module2-color: #a78bfa;
    --module3-color: #f472b6;
    --module4-color: #fbbf24;
    --module5-color: #34d399;
    --module6-color: #22d3ee;
    --bg-color: #0f0f0f;
    --panel-bg: #1e1e1e;
    --border-color: #444;
    --text-color: #e0e0e0;
    --text-secondary: #a0a0a0;
    --code-bg: #2a2a2a;
    --repl-bg: #1e1e1e;
    --repl-input-bg: #2a2a2a;
    --repl-text: #e0e0e0;
    --header-gradient-start: #5865f2;
    --header-gradient-end: #a855f7;
    
    /* Safe area support for iOS */
    --safe-area-top: env(safe-area-inset-top);
    --safe-area-bottom: env(safe-area-inset-bottom);
    --safe-area-left: env(safe-area-inset-left);
    --safe-area-right: env(safe-area-inset-right);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    -webkit-user-select: none;
    -webkit-touch-callout: none;
    -webkit-tap-highlight-color: transparent;
    user-select: none;
    color: var(--text-color);
    line-height: 1.6;
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    margin: 0;
    padding: 0;
    transition: background-color 0.3s ease, color 0.3s ease;
    min-width: 0;
    width: 100%;
}

/* Key terms styling for exercises */
.key-term {
    font-weight: bold;
    color: #fbbf24;
}

/* Challenge headings styling for exercises */
.challenge-heading {
    font-weight: bold;
    color: #10b981;
    font-size: 1.1em;
}

/* Prevent iOS viewport scrolling when menu is open */
html.menu-open,
body.menu-open {
    overflow: hidden;
    width: 100%;
    height: 100vh;
    position: relative;
}

html.menu-open {
    background-color: var(--bg-color);
}

/* Header - sticky at top */
header {
    padding: 12px 20px;
    padding-top: calc(12px + var(--safe-area-top, 0px));
    padding-left: max(20px, var(--safe-area-left, 0px));
    padding-right: max(20px, var(--safe-area-right, 0px));
    background: linear-gradient(135deg, var(--header-gradient-start), var(--header-gradient-end));
    color: white;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.15);
    flex-shrink: 0;
    z-index: 100;
}

/* Desktop shows full text, mobile shows abbreviated */
.mobile-text {
    display: none;
}

.desktop-text {
    display: inline;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
    min-width: 0;
}

.logo-container {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 0;
    min-width: 0;
    flex-shrink: 1;
}

.logo {
    height: 40px;
    width: auto;
    display: block;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.3));
}

header h1 {
    font-size: 1.8em;
    margin: 0;
    min-width: 0;
    word-break: break-word;
}

.subtitle {
    font-size: 1.1em;
    opacity: 0.95;
}

/* Hamburger Menu */
.menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    height: calc(100vh + env(safe-area-inset-bottom));
    background: rgba(0, 0, 0, 0.5);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    z-index: 999;
    touch-action: none;
}

.menu-overlay.visible {
    opacity: 1;
    visibility: visible;
}

.menu-panel {
    position: fixed;
    top: 0;
    right: -320px;
    width: 320px;
    max-width: 85vw;
    height: 100vh;
    height: calc(100vh + env(safe-area-inset-bottom));
    background: var(--panel-bg);
    box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
    transition: right 0.3s ease;
    z-index: 1000;
    display: flex;
    flex-direction: column;
    padding-top: var(--safe-area-top, 0px);
    padding-bottom: env(safe-area-inset-bottom);
    overflow-y: auto;
    overscroll-behavior: contain;
    -webkit-overflow-scrolling: touch;
}

.menu-panel.open {
    right: 0;
}

.menu-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    border-bottom: 2px solid var(--border-color);
}

.menu-header h2 {
    color: var(--primary-color);
    font-size: 1.5em;
    margin: 0;
}

.menu-items {
    flex: 1;
    overflow-y: auto;
    padding: 10px 0;
}

.menu-item {
    width: 100%;
    padding: 16px 20px;
    background: none;
    border: none;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 1em;
    cursor: pointer;
    transition: background-color 0.2s ease;
    display: flex;
    align-items: center;
    gap: 12px;
    text-align: left;
}

.menu-item:hover {
    background: var(--primary-color);
    color: white;
}

.menu-item svg {
    flex-shrink: 0;
}

.menu-item span {
    flex: 1;
}

/* Active state for exercise toggle */
#toggleExercises.active svg {
    stroke: var(--success-color);
}

#toggleExercises.active svg path,
#toggleExercises.active svg rect {
    stroke: var(--success-color);
}

/* Expandable menu items */
.menu-item-group {
    border-bottom: 1px solid var(--border-color);
}

.menu-item-expandable {
    position: relative;
}

.menu-item-expandable .expand-icon {
    transition: transform 0.3s ease;
    margin-left: auto;
}

.menu-item-expandable.expanded .expand-icon {
    transform: rotate(180deg);
}

.submenu {
    max-height: 0;
    overflow-y: auto;
    transition: max-height 0.3s ease;
    background: var(--code-bg);
    -webkit-overflow-scrolling: touch;
}

.submenu.expanded {
    max-height: 1200px;
}

.submenu-item {
    width: 100%;
    padding: 12px 20px 12px 52px;
    background: none;
    border: none;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 0.95em;
    cursor: pointer;
    transition: background-color 0.2s ease;
    display: block;
    text-align: left;
}

.submenu-item:hover {
    background: var(--primary-color);
    color: white;
}

.submenu-item:last-child {
    border-bottom: none;
}

/* About Overlay */
.about-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    z-index: 1001;
    padding: 20px;
}

.about-overlay.visible {
    opacity: 1;
    visibility: visible;
}

.about-modal {
    background: var(--panel-bg);
    border-radius: 10px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    max-width: 600px;
    width: 100%;
    max-height: 80vh;
    display: flex;
    flex-direction: column;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        transform: translateY(20px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.about-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 25px;
    border-bottom: 2px solid var(--border-color);
}

.about-header h2 {
    color: var(--primary-color);
    font-size: 1.5em;
    margin: 0;
}

.about-content {
    padding: 25px;
    overflow-y: auto;
    line-height: 1.8;
}

.about-content p {
    margin-bottom: 1em;
    color: var(--text-color);
}

.about-content ul {
    margin: 1em 0;
    padding-left: 1.5em;
}

.about-content li {
    margin-bottom: 0.5em;
    color: var(--text-color);
}

.about-content strong {
    color: var(--primary-color);
    font-weight: 600;
}

.about-footer {
    margin-top: 1.5em;
    padding-top: 1em;
    border-top: 1px solid var(--border-color);
    font-size: 0.9em;
    color: var(--text-secondary);
}

/* Welcome Modal */
.welcome-modal {
    max-width: 500px;
}

.welcome-header {
    justify-content: center;
    gap: 12px;
}

.welcome-logo {
    width: 40px;
    height: 40px;
    object-fit: contain;
}

.inline-icon {
    vertical-align: middle;
    margin: 0 4px;
    color: var(--primary-color);
}

.welcome-content {
    text-align: center;
    padding: 30px 25px;
}

.welcome-content p {
    font-size: 1.1em;
    margin-bottom: 1.5em;
    color: var(--text-color);
}

.welcome-detail {
    font-size: 1em !important;
    margin-bottom: 0.5em !important;
    color: var(--text-color);
}

.welcome-detail strong {
    color: var(--primary-color);
}

.version-text {
    font-size: 0.95em;
    color: var(--text-secondary);
    margin-bottom: 2em !important;
}

.welcome-content .btn-primary {
    padding: 12px 40px;
    font-size: 1.1em;
    margin-bottom: 1.5em;
    width: auto;
    display: inline-block;
}

.welcome-checkbox {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    margin-top: 1em;
}

.welcome-checkbox input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.welcome-checkbox label {
    color: var(--text-color);
    cursor: pointer;
    font-size: 0.95em;
}

.about-footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
}

.about-footer a:hover {
    text-decoration: underline;
}

/* Built-in Functions specific styling */
.builtins-content h3 {
    color: var(--primary-color);
    margin-top: 1.5em;
    margin-bottom: 0.5em;
    font-size: 1.1em;
}

.builtins-content h3:first-child {
    margin-top: 0;
}

.builtins-content code {
    background: var(--code-bg);
    padding: 0.15rem 0.4rem;
    border-radius: 3px;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 0.9em;
    color: var(--primary-color);
    font-weight: 600;
}

.builtins-content ul {
    margin: 0.5em 0;
}

.builtins-content li {
    margin-bottom: 0.4em;
    line-height: 1.6;
}

/* Main container for content between header and footer */
.main-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* Main content - three column grid */
.main-content {
    flex: 1;
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 0;
    overflow: hidden;
}

/* When exercises shown - three columns */
.main-content.exercises-visible {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr) minmax(0, 1fr);
}

/* Prevent scrolling main content when menu is open */
body.menu-open header,
body.menu-open .main-content {
    touch-action: none;
    overflow: hidden !important;
}

body.menu-open .column {
    touch-action: none;
    pointer-events: none;
    overflow: hidden !important;
}

body.menu-open .output,
body.menu-open .repl-history {
    overflow: hidden !important;
}

/* Column containers */
.column {
    display: flex;
    flex-direction: column;
    overflow: hidden;
    border-right: 1px solid var(--border-color);
    min-width: 0;
}

.column:last-child {
    border-right: none;
}

.definitions-column,
.repl-column,
.exercises-column {
    height: 100%;
}



/* Exercise Selector Bar */
.mobile-exercise-nav {
    display: none;
    background: var(--panel-bg);
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    padding: 15px;
    justify-content: space-between;
    align-items: center;
    gap: 15px;
    margin-bottom: 20px;
}

.nav-arrow {
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 6px;
    padding: 8px 16px;
    font-size: 1.2em;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.2s ease;
    min-width: 60px;
}

.nav-arrow:hover:not(:disabled) {
    background: var(--secondary-color);
    transform: scale(1.05);
}

.nav-arrow:disabled {
    background: var(--border-color);
    color: var(--text-secondary);
    cursor: not-allowed;
    opacity: 0.5;
}

.exercise-label {
    font-size: 1.1em;
    font-weight: 600;
    color: var(--text-color);
    text-align: center;
    flex: 1;
}

.exercise-label.completed {
    color: var(--success-color);
}

.exercise-selector-bar {
    background: var(--panel-bg);
    padding: 15px;
    display: flex;
    flex-direction: column;
    gap: 15px;
    flex-shrink: 0;
}

.exercise-header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.exercise-header-row h2 {
    color: var(--primary-color);
    font-size: 1.3em;
    margin: 0;
}

.exercise-header-row #resetProgress {
    min-width: 32px;
    padding: 4px 8px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.exercise-header-row #resetProgress svg {
    display: block;
}

.exercise-buttons-wrapper {
    width: 100%;
}

.exercise-buttons-container {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: center;
    justify-content: center;
}

.exercise-btn {
    width: 40px;
    height: 40px;
    padding: 0;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    background-color: var(--panel-bg);
    color: var(--text-color);
    font-size: 0.95em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.exercise-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.exercise-btn.completed {
    background-color: var(--success-color);
    border-color: var(--success-color);
    color: white;
}

.exercise-btn.active {
    box-shadow: 0 0 0 4px rgba(139, 155, 255, 0.8);
}

.module-separator {
    width: 1px;
    height: 30px;
    background-color: var(--border-color);
    margin: 0 4px;
}

/* Code and REPL side by side */
.panel {
    background: var(--panel-bg);
    padding: 20px;
    display: flex;
    flex-direction: column;
    transition: background-color 0.3s ease;
    min-width: 0;
    overflow-x: auto;
    overflow-y: hidden;
    flex: 1;
    height: 100%;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--border-color);
    min-width: 0;
    flex-shrink: 0;
}

.panel-header h2 {
    color: var(--primary-color);
    font-size: 1.3em;
    min-width: 0;
    word-break: break-word;
}

.output-container {
    position: relative;
}

.output-container .output {
    padding-right: 100px;
}

.clear-editor-btn {
    position: absolute;
    top: 18px;
    right: 0;
    z-index: 10;
}

.btn {
    padding: 8px 16px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.95em;
    font-weight: 600;
    transition: all 0.3s ease;
    min-width: 0;
    white-space: normal;
    word-break: break-word;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(94, 53, 177, 0.3);
}

.button-group {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    min-width: 0;
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-color);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: var(--border-color);
}

/* Hamburger menu button - subtle neon styling */
#menuToggle,
#closeMenu {
    background: rgba(251, 191, 36, 0.55);
    border: 2px solid rgba(251, 191, 36, 0.9);
    color: white;
    backdrop-filter: blur(4px);
}

#menuToggle:hover,
#closeMenu:hover {
    background: rgba(251, 191, 36, 0.7);
    border-color: rgba(251, 191, 36, 1);
    box-shadow: 0 0 12px rgba(251, 191, 36, 0.6);
}

/* Modal close buttons - same golden styling as hamburger */
#closeAbout,
#closeBuiltins {
    background: rgba(251, 191, 36, 0.55);
    border: 2px solid rgba(251, 191, 36, 0.9);
    color: white;
    backdrop-filter: blur(4px);
}

#closeAbout:hover,
#closeBuiltins:hover {
    background: rgba(251, 191, 36, 0.7);
    border-color: rgba(251, 191, 36, 1);
    box-shadow: 0 0 12px rgba(251, 191, 36, 0.6);
}

.btn-danger {
    background-color: #e67e22;
    color: white;
}

.btn-danger:hover {
    background-color: #d35400;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(230, 126, 34, 0.3);
}

.btn-small {
    padding: 6px 12px;
    font-size: 0.85em;
}

/* CodeMirror integration */
.CodeMirror {
    height: 100%;
    min-height: 300px;
    flex: 1;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace !important;
    font-size: 14px;
    line-height: 1.5;
    background-color: var(--repl-bg) !important;
    overflow: auto;
    max-width: 100%;
    min-width: 0; /* Allow shrinking below content width */
}

.CodeMirror-focused {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(94, 53, 177, 0.1);
}

#codeEditor {
    display: none; /* Hide the original textarea */
}

.output {
    margin-top: 15px;
    padding: 12px;
    border-radius: 5px;
    font-size: 0.95em;
}

#editorOutput {
    background-color: var(--repl-bg);
    min-height: 60px;
    padding: 10px;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    transition: background-color 0.3s ease;
}

.success {
    color: var(--success-color);
    font-weight: 600;
    margin-bottom: 8px;
}

.error {
    color: var(--error-color);
    font-weight: 600;
    margin-bottom: 8px;
}

.info {
    color: var(--text-secondary);
    font-style: italic;
}

/* REPL Styles */

.repl-panel .panel-header h2 {
    color: var(--primary-color);
}

.repl-history {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    min-height: 300px;
    padding: 10px;
    background-color: var(--repl-bg);
    border-radius: 5px;
    margin-bottom: 15px;
    user-select: text;
    -webkit-user-select: text;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    transition: background-color 0.3s ease;
}

.repl-entry {
    overflow-wrap: break-word;
    margin-bottom: 8px;
}

.repl-prompt {
    color: var(--primary-color);
    font-weight: bold;
    margin-right: 5px;
}

.repl-input {
    color: var(--repl-text);
}

.repl-input-code,
.repl-output-code {
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace !important;
    font-size: 14px;
    line-height: 1.5;
}

/* Force consistent font rendering across all code elements */
.repl-input-code *,
.repl-output-code * {
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace !important;
}

.repl-input-code {
    display: inline-block;
    max-width: 100%;
    white-space: pre-wrap;
    word-wrap: break-word;
    color: var(--repl-text);
}

.repl-result {
    margin-left: 20px;
    margin-bottom: 12px;
}

.repl-output-code {
    display: block;
    white-space: pre-wrap;
    word-wrap: break-word;
    overflow-wrap: break-word;
    word-break: break-all;
    max-width: 100%;
}

.repl-error {
    color: var(--error-color);
    margin-left: 20px;
    margin-bottom: 12px;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
}

.repl-warning {
    color: #fbbf24 !important;
    margin-left: 20px;
    margin-bottom: 12px;
    font-style: italic;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
}

.repl-warning * {
    color: #fbbf24 !important;
}

.repl-info,
.repl-result {
    color: var(--success-color);
    margin-left: 20px;
    margin-bottom: 12px;
    font-style: italic;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
}

.repl-input-container {
    display: flex;
    align-items: flex-start;
    background-color: var(--repl-input-bg);
    border: 2px solid var(--border-color);
    border-radius: 5px;
    padding: 8px;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.repl-input-container:focus-within {
    border-color: var(--primary-color);
}

#replInputWrapper {
    flex: 1;
}

#replInputWrapper .CodeMirror {
    border: none;
    height: auto;
    min-height: 20px;
    background: var(--repl-input-bg) !important;
}

#replInputWrapper .CodeMirror-scroll {
    min-height: 20px;
    max-height: 150px;
}

#replInput {
    display: none; /* Hide the original textarea */
}

/* Examples Panel */
.examples-panel {
    background: var(--panel-bg);
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    padding: 20px;
}

.examples-panel h2 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 1.3em;
}

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 10px;
}

.example-btn {
    padding: 12px;
    background-color: var(--code-bg);
    border: 2px solid var(--border-color);
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.95em;
    font-weight: 600;
    color: var(--text-color);
    transition: all 0.3s ease;
}

.example-btn:hover {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(94, 53, 177, 0.2);
}

footer {
    margin-top: 20px;
    padding: 12px 20px;
    background: linear-gradient(135deg, var(--header-gradient-start), var(--header-gradient-end));
    color: rgba(255, 255, 255, 0.9);
    font-size: 0.9em;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.15);
}

.footer-content {
    text-align: left;
}

footer p {
    margin: 0;
}

footer a {
    color: white;
    text-decoration: underline;
    transition: color 0.3s ease;
}

footer a:hover {
    color: #e0e0e0;
}

/* Responsive Design */

/* Intermediate breakpoint when exercises are visible (3 columns) */
@media (max-width: 1400px) {
    body.exercises-visible .desktop-text {
        display: none;
    }
    
    body.exercises-visible .mobile-text {
        display: inline;
    }
}

@media (max-width: 1015px) {
    body {
        height: 100vh; /* Fixed height when exercises hidden */
        overflow: hidden; /* No body scroll when exercises hidden */
    }
    
    body.exercises-visible {
        height: auto; /* Allow body to expand */
        min-height: 100vh;
        overflow: auto; /* Allow scroll when exercises shown */
    }
    
    .main-container {
        overflow: visible;
        min-height: calc(100vh - var(--safe-area-top, 0px) - 50px); /* Account for safe area + header */
    }
    
    /* Show mobile text, hide desktop text */
    .desktop-text {
        display: none;
    }
    
    .mobile-text {
        display: inline;
    }
    
    /* Adjust header for mobile with safe areas */
    header {
        padding: 8px 15px !important;
        padding-top: calc(8px + var(--safe-area-top, 0px)) !important;
        padding-left: max(15px, var(--safe-area-left, 0px)) !important;
        padding-right: max(15px, var(--safe-area-right, 0px)) !important;
    }
    
    .main-content {
        grid-template-columns: 1fr;
        display: flex;
        flex-direction: column;
        overflow: visible;
        gap: 0;
        padding: 0;
    }
    
    .column {
        border-right: none;
    }
    
    /* Function and REPL columns take full viewport height */
    .definitions-column,
    .repl-column {
        height: calc((100vh - 50px - var(--safe-area-top, 0px)) / 2) !important; /* Account for header + safe area */
        flex-shrink: 0;
        overflow: hidden;
    }
    
    /* Add visible divider between stacked panels */
    .definitions-column {
        border-top: 2px solid var(--border-color) !important;
    }
    
    /* In browser mode on iPad (not standalone PWA), reduce height to account for Safari chrome + tab bar */
    body.ipad-device:not(.standalone-mode) .definitions-column,
    body.ipad-device:not(.standalone-mode) .repl-column {
        height: calc((100vh - 130px - var(--safe-area-top, 0px)) / 2) !important; /* Extra space for browser chrome + tab bar */
    }
    
    /* Exercises column goes below - scrollable */
    .exercises-column {
        height: auto !important;
        min-height: 100vh;
    }
    
    .panel {
        height: 100% !important;
        max-height: none !important;
        min-height: 0 !important;
        display: flex;
        flex-direction: column;
        overflow: hidden;
        padding: 15px; /* Reduce padding on mobile */
    }
    
    .panel-header {
        flex-shrink: 0;
    }
    
    /* CodeMirror container takes remaining space and scrolls */
    .editor-panel > textarea {
        flex: 1 1 auto;
        min-height: 0;
        height: 0; /* Force flex to control height */
    }
    
    .editor-panel .CodeMirror {
        height: 100% !important;
        max-height: none !important;
        min-height: 0 !important;
    }
    
    .editor-panel .CodeMirror-scroll {
        min-height: 0 !important;
    }
    
    /* REPL history scrolls */
    .repl-history {
        flex: 1 1 0;
        min-height: 0;
        overflow-y: auto !important;
    }
    
    /* Output and input areas don't shrink - always visible */
    .output-container,
    .repl-input-container {
        flex-shrink: 0;
        flex-grow: 0;
        min-height: 0;
    }
    
    /* Remove max-height so no scrollbar needed */
    .output-container .output {
        overflow-y: visible;
    }
    
    .output-container {
        padding-bottom: 0;
    }
    
    header {
        padding: 8px 15px; /* Smaller padding on mobile */
    }
    
    header h1 {
        font-size: 1.4em; /* Smaller font on mobile */
    }
    
    .logo {
        height: 28px; /* Smaller logo on mobile */
    }
}

/* Scrollbar Styling */
.repl-history::-webkit-scrollbar {
    width: 8px;
}

.repl-history::-webkit-scrollbar-track {
    background: var(--repl-bg);
}

.repl-history::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.repl-history::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* Syntax Highlighting Color Overrides for Monokai (Dark Theme) */
:root {
    --syntax-keyword: #F92672;
    --syntax-function: #A6E22E;
    --syntax-string: #E6DB74;
    --syntax-number: #AE81FF;
    --syntax-comment: #75715E;
    --syntax-operator: #F92672;
    --syntax-variable: #66D9EF;
}

/* Force wrapping for all CodeMirror spans in REPL */
.repl-output-code span,
.repl-input-code span {
    white-space: pre-wrap !important;
    word-break: break-all !important;
    word-wrap: break-word !important;
}

/* Exercises Section */
.exercises-section {
    background: var(--panel-bg);
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    padding: 20px;
    transition: background-color 0.3s ease;
}

.exercises-header {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    text-align: center;
}

.exercises-tip {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    font-size: 0.85rem;
}

.module {
    background: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    margin-bottom: 0.75rem;
    overflow: hidden;
    transition: all 0.2s ease;
}

.module:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    transform: translateY(-1px);
    border-color: var(--primary-color);
}

.module-header {
    padding: 0.875rem 1rem;
    background: var(--panel-bg);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    user-select: none;
    transition: all 0.2s ease;
}

.module-header:hover {
    background: linear-gradient(90deg, rgba(88, 101, 242, 0.08), rgba(168, 85, 247, 0.08));
}

.module.active .module-header {
    background: linear-gradient(90deg, rgba(88, 101, 242, 0.15), rgba(168, 85, 247, 0.15));
    border-bottom: 2px solid var(--primary-color);
}

.module.active .module-title {
    color: var(--primary-color);
    font-weight: 700;
}

.module.active .module-progress {
    color: var(--primary-color);
    font-weight: 600;
}

.module-toggle {
    font-size: 0.875rem;
    transition: transform 0.3s ease;
    color: var(--primary-color);
    font-weight: bold;
}

.module.collapsed .module-toggle {
    transform: rotate(-90deg);
}

.module-title {
    flex: 1;
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-color);
}

.module-progress {
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 500;
}

.module-content {
    padding: 0.25rem 0;
    border-top: 1px solid var(--border-color);
    max-height: 1000px;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
}

.module.collapsed .module-content {
    max-height: 0;
    padding: 0;
    border-top: none;
}

.exercise {
    padding: 0.625rem 1rem 0.625rem 2.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    transition: all 0.2s ease;
    position: relative;
}

.exercise:hover {
    background: linear-gradient(90deg, rgba(88, 101, 242, 0.12), rgba(168, 85, 247, 0.12));
    transform: translateX(2px);
}

.exercise.selected {
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    color: white;
    box-shadow: 0 2px 8px rgba(88, 101, 242, 0.3);
    transform: translateX(4px);
    border-left: 3px solid rgba(255, 255, 255, 0.5);
}

.exercise.selected .exercise-number,
.exercise.selected .exercise-title {
    color: white;
    font-weight: 600;
}

.exercise.selected.completed .exercise-status {
    border-color: white !important;
}

.exercise.selected.completed .exercise-title {
    color: rgba(255, 255, 255, 0.85);
}

.exercise-status {
    position: absolute;
    left: 0.875rem;
    width: 18px;
    height: 18px;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background-color: transparent;
    border: 2px solid #dc3545;
    overflow: hidden;
    text-indent: -9999px;
}

.exercise-status::before {
    content: '';
    position: absolute;
    text-indent: 0;
}

.exercise-status:hover {
    transform: scale(1.15);
}

.exercise.completed .exercise-status {
    border-radius: 3px;
    background-color: #28a745;
    border-color: #28a745;
}

.exercise.completed .exercise-status::before {
    content: '✓';
    font-weight: bold;
    font-size: 12px;
    color: white;
}

.exercise-number {
    color: var(--text-secondary);
    font-weight: 600;
    min-width: 1.5rem;
    font-size: 0.875rem;
}

.exercise-title {
    color: var(--text-color);
    flex: 1;
    font-size: 0.9rem;
}

.exercise.completed .exercise-title {
    color: var(--text-secondary);
    text-decoration: line-through;
}

/* Exercise Content Panel */
.exercise-content-panel {
    overflow-y: auto;
    flex: 1;
    border-top: 2px solid var(--border-color);
}



.exercise-content-panel .panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.exercise-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.hints-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}



.completion-toggle {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    user-select: none;
    font-size: 0.9rem;
    color: var(--text-color);
}

.completion-text-short {
    display: none;
}

.completion-toggle input[type="checkbox"] {
    cursor: pointer;
    width: 18px;
    height: 18px;
    accent-color: var(--primary-color);
}

.completion-toggle:hover {
    color: var(--primary-color);
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.exercise-content {
    line-height: 1.5;
    color: var(--text-color);
    padding-bottom: 60px; /* Extra padding to ensure content is scrollable to bottom */
    user-select: text;
    -webkit-user-select: text;
}

.exercise-content h3 {
    color: var(--primary-color);
    margin-top: 1rem;
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
}

.exercise-content p {
    margin-bottom: 1rem;
    margin-top: 0;
}

.exercise-content .spacer {
    height: 1rem;
    display: block;
}

.exercise-content code {
    background: var(--code-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 3px;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
    font-size: 0.9em;
    color: #00bcd4; /* Bright cyan for better readability */
}

.exercise-content pre {
    background: var(--code-bg);
    padding: 1rem;
    border-radius: 5px;
    overflow-x: auto;
    margin: 1rem 0;
    border-left: 4px solid var(--nested-highlight);
    white-space: pre;
}

.exercise-content pre code {
    background: transparent;
    padding: 0;
    color: var(--text-color);
    white-space: pre;
}

.exercise-content ul, .exercise-content ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

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

.exercise-content .hint {
    background: linear-gradient(135deg, rgba(88, 101, 242, 0.1), rgba(168, 85, 247, 0.1));
    padding: 1rem;
    border-radius: 5px;
    border-left: 4px solid var(--nested-highlight);
    margin: 1rem 0;
}

.exercise-content .hint strong {
    color: var(--primary-color);
}

#closeExercise,
#toggleExercisePanel {
    min-width: 32px;
    padding: 4px 8px;
}

/* Responsive design for exercises */
@media (max-width: 768px) {
    .exercises-section {
        margin: 0;
    }

    .exercises-header {
        font-size: 1.5rem;
    }

    .module-header {
        padding: 0.875rem 1rem;
    }

    .exercise {
        padding: 0.625rem 1rem 0.625rem 2.5rem;
    }

    .exercise-status {
        left: 1rem;
        font-size: 1rem;
    }
    
    .exercise-content-panel .panel-header {
        flex-wrap: wrap;
        gap: 0.5rem;
    }
    
    .exercise-content-panel .panel-header h2 {
        font-size: 1.1rem;
    }
    
    .exercise-controls {
        justify-content: flex-end;
        gap: 0.5rem;
        flex-shrink: 0;
    }
    
    .completion-toggle {
        font-size: 0.85rem;
    }
}



@media (max-width: 1024px) {
    /* Remove restrictive max-heights for mobile */
    
    .exercise-buttons-container {
        justify-content: center;
    }
}

@media (max-width: 768px) {
    .mobile-exercise-nav {
        display: none;
    }
    
    .exercise-selector-bar {
        display: flex;
    }
    
    header {
        padding: 10px;
        margin-bottom: 10px;
    }
    
    .logo {
        height: 32px;
    }
    
    header h1 {
        font-size: 1.5em;
    }
    
    .logo-container {
        gap: 8px;
        margin-bottom: 0;
        justify-content: center;
    }
    
    .header-content {
        text-align: center;
    }
    
    .exercise-btn {
        width: 28px;
        height: 28px;
        font-size: 0.75em;
    }
    
    .completion-text-full {
        display: none;
    }
    
    .completion-text-short {
        display: inline;
    }
    
    .module-separator {
        display: none;
    }
    
    footer {
        flex-direction: column;
        text-align: center;
    }
}

/* Mobile layout reorganization */
@media (max-width: 768px) {
    .main-content {
        grid-template-columns: 1fr !important;
    }
    
    .left-column {
        order: 2;
    }
    
    .right-column {
        order: 1;
    }
    
    .output-container .output {
        padding-right: 10px;
        word-wrap: break-word;
    }
    
    .clear-editor-btn {
        position: static;
        display: block;
        width: 100%;
        margin-top: 10px;
    }
}