@import url('https://fonts.googleapis.com/css2?family=Nunito:wght@400;600;700;800&display=swap');

/* === Design Tokens === */
:root {
    --color-primary: #6366f1;
    --color-primary-light: #818cf8;
    --color-primary-dark: #4f46e5;
    --color-success: #10b981;
    --color-success-light: #d1fae5;
    --color-error: #ef4444;
    --color-error-light: #fee2e2;
    --color-warning: #f59e0b;
    --color-warning-light: #fef3c7;
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-text: #1e293b;
    --color-text-muted: #64748b;
    --color-border: #e2e8f0;
    --color-border-light: #f1f5f9;

    --color-grade2: #f43f5e;
    --color-grade3: #14b8a6;
    --color-grade4: #f59e0b;
    --color-grade5: #6366f1;

    --font-family: 'Nunito', 'Quicksand', system-ui, -apple-system, sans-serif;

    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-6: 24px;
    --space-8: 32px;
    --space-12: 48px;

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
    --shadow-lg: 0 8px 24px rgba(0,0,0,0.1);
    --shadow-xl: 0 12px 40px rgba(0,0,0,0.12);

    --transition: all 0.2s ease;
    --max-width: 1200px;
}

/* === Dark Mode Tokens === */
body.dark-mode {
    --color-bg: #0f172a;
    --color-surface: #1e293b;
    --color-text: #f1f5f9;
    --color-text-muted: #94a3b8;
    --color-border: #334155;
    --color-border-light: #1e293b;
    --color-success-light: #064e3b;
    --color-error-light: #7f1d1d;
    --color-warning-light: #78350f;
}

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

/* === Loading States === */
.loading {
    pointer-events: none;
    opacity: 0.6;
    position: relative;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 32px;
    height: 32px;
    margin: -16px 0 0 -16px;
    border: 3px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* === Error / Success Messages === */
.error-message {
    background: var(--color-error);
    color: white;
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-md);
    margin: var(--space-2) 0;
    display: flex;
    align-items: center;
    gap: var(--space-2);
    animation: shake 0.3s ease;
    font-family: var(--font-family);
}

.error-message::before {
    content: '⚠️';
    font-size: 1.3em;
}

.success-message {
    background: var(--color-success);
    color: white;
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-md);
    margin: var(--space-2) 0;
    display: flex;
    align-items: center;
    gap: var(--space-2);
    animation: fadeIn 0.3s ease;
    font-family: var(--font-family);
}

.success-message::before {
    content: '✅';
    font-size: 1.3em;
}

/* === Accessibility === */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--color-primary);
    color: white;
    padding: var(--space-2) var(--space-4);
    text-decoration: none;
    border-radius: 0 0 var(--radius-sm) 0;
    z-index: 100;
    font-family: var(--font-family);
}

.skip-link:focus {
    top: 0;
}

*:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* === Body === */
body {
    font-family: var(--font-family);
    background: var(--color-bg);
    color: var(--color-text);
    min-height: 100vh;
    padding: var(--space-4);
    margin: 0;
    transition: background 0.3s ease, color 0.3s ease;
}

/* === Dark Mode Overrides === */
body.dark-mode .container {
    background: rgba(30, 41, 59, 0.95);
    border: 1px solid var(--color-border);
}

body.dark-mode .history-sidebar {
    background: rgba(30, 41, 59, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-right: 1px solid var(--color-border);
}

body.dark-mode .problem-container {
    background: var(--color-surface) !important;
    border: 1px solid var(--color-border);
}

body.dark-mode .mountain-top,
body.dark-mode .base-number {
    background: var(--color-surface);
    border-color: var(--color-border);
}

body.dark-mode .word-problem-card {
    background: var(--color-surface);
}

body.dark-mode .word-problem-text {
    background: rgba(99, 102, 241, 0.1);
}

body.dark-mode .settings-panel {
    background: var(--color-surface);
}

body.dark-mode .history-item {
    background: var(--color-surface);
    border-color: var(--color-border);
}

body.dark-mode .history-item-type {
    color: var(--color-text);
}

body.dark-mode .history-item-date,
body.dark-mode .history-item-details,
body.dark-mode .no-history {
    color: var(--color-text-muted);
}

body.dark-mode .control-group label {
    color: var(--color-text);
}

body.dark-mode .word-problem-answer label {
    color: var(--color-text);
}

body.dark-mode .difficulty-select,
body.dark-mode .problem-count-input {
    background: var(--color-surface);
    color: var(--color-text);
    border-color: var(--color-border);
}

body.dark-mode .answer-input {
    background: var(--color-surface);
    color: var(--color-text);
    border-color: var(--color-border);
}

body.dark-mode .word-problem-answer input {
    background: var(--color-surface);
    color: var(--color-text);
    border-color: var(--color-border);
}

body.dark-mode .word-problem-explanation {
    background: rgba(51, 65, 85, 0.5);
    color: var(--color-text);
}

body.dark-mode .tracing-container {
    background: var(--color-surface);
}

body.dark-mode .tracing-header {
    border-bottom-color: var(--color-border);
}

body.dark-mode .tracing-progress {
    color: var(--color-text);
}

body.dark-mode .picture-label {
    color: var(--color-text);
}

body.dark-mode .analytics-panel {
    background: rgba(99, 102, 241, 0.1);
    color: var(--color-text);
}

body.dark-mode .analytics-panel h3 {
    color: var(--color-primary-light);
}

body.dark-mode .analytics-panel p {
    color: var(--color-text);
}

body.dark-mode .analytics-panel strong {
    color: var(--color-primary-light);
}

body.dark-mode .shortcut-hint {
    color: var(--color-text-muted);
}

/* === Layout === */
.app-wrapper {
    display: flex;
    gap: var(--space-6);
    max-width: var(--max-width);
    margin: 0 auto;
}

/* === Sidebar === */
.history-sidebar {
    width: 280px;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: var(--radius-xl);
    padding: var(--space-6);
    border: 1px solid var(--color-border);
    max-height: calc(100vh - 32px);
    overflow-y: auto;
    flex-shrink: 0;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-6);
    padding-bottom: var(--space-4);
    border-bottom: 1px solid var(--color-border);
}

.sidebar-header h2 {
    font-size: 1.15em;
    font-weight: 700;
    color: var(--color-primary);
    margin: 0;
}

.btn-clear-history {
    background: var(--color-error-light);
    color: var(--color-error);
    border: none;
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 1.1em;
    transition: var(--transition);
}

.btn-clear-history:hover {
    background: var(--color-error);
    color: white;
}

.history-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.no-history {
    text-align: center;
    color: var(--color-text-muted);
    font-style: italic;
    padding: var(--space-6);
    font-size: 0.95em;
}

.history-item {
    background: var(--color-surface);
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-3) var(--space-4);
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}

.history-item:hover {
    border-color: var(--color-primary-light);
    box-shadow: var(--shadow-sm);
}

.history-item.active {
    border-color: var(--color-primary);
    background: rgba(99, 102, 241, 0.05);
}

.history-item-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-1);
}

.history-item-type {
    font-weight: 700;
    color: var(--color-text);
    font-size: 0.95em;
}

.history-item-date {
    font-size: 0.75em;
    color: var(--color-text-muted);
}

.history-item-score {
    font-size: 1em;
    font-weight: 700;
    margin: var(--space-1) 0;
}

.history-item-score.perfect { color: var(--color-success); }
.history-item-score.good { color: var(--color-primary); }
.history-item-score.okay { color: var(--color-warning); }
.history-item-score.needs-work { color: var(--color-error); }

.history-item-details {
    font-size: 0.85em;
    color: var(--color-text-muted);
}

/* === District Selector === */
.district-panel {
    background: linear-gradient(135deg, var(--color-surface) 0%, rgba(99, 102, 241, 0.05) 100%);
    border-radius: var(--radius-md);
    padding: var(--space-4);
    margin-bottom: var(--space-4);
    border: 1.5px solid var(--color-primary-light);
}

.district-panel h3 {
    color: var(--color-primary);
    margin-bottom: var(--space-3);
    font-size: 1em;
    font-weight: 700;
}

.district-panel label {
    display: block;
    font-size: 0.8em;
    font-weight: 600;
    color: var(--color-text-muted);
    margin-bottom: var(--space-1);
    margin-top: var(--space-2);
}

.district-panel label:first-of-type {
    margin-top: 0;
}

.district-select {
    width: 100%;
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-sm);
    border: 1.5px solid var(--color-border);
    background: var(--color-surface);
    color: var(--color-text);
    font-family: var(--font-family);
    font-size: 0.85em;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-sizing: border-box;
}

.district-select:hover {
    border-color: var(--color-primary-light);
}

.district-select:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.district-select:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Searchable Select Component */
.searchable-select {
    position: relative;
    width: 100%;
}

.ss-input {
    padding-right: 28px !important;
}

.ss-clear {
    position: absolute;
    right: 8px;
    top: 50%;
    transform: translateY(-50%);
    cursor: pointer;
    color: var(--color-text-muted);
    font-size: 1.2em;
    line-height: 1;
    z-index: 2;
    width: 18px;
    height: 18px;
    text-align: center;
    border-radius: 50%;
    transition: var(--transition);
}
.ss-clear:hover {
    color: var(--color-error);
    background: rgba(239, 68, 68, 0.1);
}

.ss-dropdown {
    display: none;
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    margin-top: 4px;
    background: var(--color-surface);
    border: 1.5px solid var(--color-primary);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-lg);
    max-height: 220px;
    overflow-y: auto;
    z-index: 100;
}
.ss-dropdown.ss-open {
    display: block;
}

.ss-group {
    padding: 6px 10px 3px;
    font-size: 0.78em;
    font-weight: 700;
    color: var(--color-primary);
    text-transform: uppercase;
    letter-spacing: 0.03em;
    position: sticky;
    top: 0;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
}

.ss-option {
    padding: 7px 12px;
    font-size: 0.85em;
    cursor: pointer;
    transition: background 0.1s;
}
.ss-option:hover, .ss-option.ss-highlight {
    background: rgba(99, 102, 241, 0.1);
    color: var(--color-primary-dark);
}
.ss-option.ss-active {
    background: rgba(99, 102, 241, 0.15);
    font-weight: 700;
    color: var(--color-primary);
}

.ss-no-results {
    padding: 12px;
    text-align: center;
    font-size: 0.85em;
    color: var(--color-text-muted);
    font-style: italic;
}

body.dark-mode .ss-dropdown {
    background: #1e293b;
    border-color: var(--color-primary);
}
body.dark-mode .ss-group {
    background: #1e293b;
    border-color: rgba(255,255,255,0.08);
}
body.dark-mode .ss-option:hover,
body.dark-mode .ss-option.ss-highlight {
    background: rgba(99, 102, 241, 0.2);
}

body.dark-mode .district-select {
    background: var(--color-surface);
    color: var(--color-text);
    border-color: var(--color-border);
}

.district-info {
    margin-top: var(--space-2);
    font-size: 0.8em;
    font-weight: 600;
    color: var(--color-primary);
    min-height: 1.2em;
}

.district-badge {
    display: none;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
    padding: 4px 14px;
    border-radius: var(--radius-full);
    font-size: 0.75em;
    font-weight: 700;
    margin-top: var(--space-2);
    letter-spacing: 0.02em;
}

/* === Streak Display === */
.streak-display {
    background: var(--color-primary);
    border-radius: var(--radius-full);
    padding: var(--space-3) var(--space-4);
    margin-bottom: var(--space-4);
    text-align: center;
    font-size: 1em;
    font-weight: 700;
    color: white;
}

/* === Settings Panel === */
.settings-panel {
    background: var(--color-surface);
    border-radius: var(--radius-md);
    padding: var(--space-4);
    margin-bottom: var(--space-4);
    border: 1px solid var(--color-border);
}

.settings-panel h3 {
    color: var(--color-primary);
    margin-bottom: var(--space-3);
    font-size: 1em;
    font-weight: 700;
}

.setting-item {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-2) 0;
    cursor: pointer;
    font-size: 0.95em;
}

/* Modern pill toggle for checkboxes */
.setting-item input[type="checkbox"] {
    appearance: none;
    -webkit-appearance: none;
    width: 44px;
    height: 24px;
    background: var(--color-border);
    border-radius: var(--radius-full);
    cursor: pointer;
    position: relative;
    transition: var(--transition);
    flex-shrink: 0;
}

.setting-item input[type="checkbox"]::after {
    content: '';
    position: absolute;
    top: 3px;
    left: 3px;
    width: 18px;
    height: 18px;
    background: white;
    border-radius: 50%;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.setting-item input[type="checkbox"]:checked {
    background: var(--color-primary);
}

.setting-item input[type="checkbox"]:checked::after {
    left: 23px;
}

.btn-export {
    width: 100%;
    margin-top: var(--space-3);
    padding: var(--space-3);
    background: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-family: var(--font-family);
    font-weight: 700;
    font-size: 0.95em;
    transition: var(--transition);
}

.btn-export:hover {
    background: var(--color-primary-dark);
    box-shadow: var(--shadow-md);
}

/* === Main Container === */
.container {
    flex: 1;
    background: var(--color-surface);
    border-radius: var(--radius-xl);
    padding: var(--space-8);
    box-shadow: var(--shadow-lg);
    min-width: 0;
    border: 1px solid var(--color-border);
}

header {
    text-align: center;
    margin-bottom: var(--space-6);
}

/* === Tab Navigation — Pill Style === */
.tab-navigation {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--space-2);
    margin-bottom: var(--space-6);
    background: var(--color-border-light);
    padding: var(--space-1);
    border-radius: var(--radius-full);
    display: inline-flex;
    margin-left: auto;
    margin-right: auto;
}

.tab-button {
    padding: var(--space-3) var(--space-4);
    font-size: 0.95em;
    font-weight: 700;
    border: none;
    background: transparent;
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: var(--transition);
    font-family: var(--font-family);
    color: var(--color-text-muted);
}

.tab-button:hover {
    background: rgba(99, 102, 241, 0.08);
    color: var(--color-primary);
}

.tab-button.active {
    background: var(--color-primary);
    color: white;
    box-shadow: var(--shadow-sm);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* === Header / Title === */
h1 {
    color: var(--color-primary);
    font-size: 2.5em;
    font-weight: 800;
    letter-spacing: -0.02em;
}

.subtitle {
    color: var(--color-text-muted);
    font-size: 1.1em;
    margin-top: var(--space-2);
    font-weight: 600;
}

/* === Controls Panel === */
.controls-panel {
    background: var(--color-surface);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    margin-bottom: var(--space-6);
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-4);
    align-items: flex-end;
    justify-content: center;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.control-group label {
    font-weight: 600;
    color: var(--color-text);
    font-size: 0.9em;
}

.difficulty-select, .problem-count-input {
    padding: var(--space-3) var(--space-4);
    font-size: 1em;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-sm);
    background: var(--color-surface);
    font-family: var(--font-family);
    cursor: pointer;
    transition: var(--transition);
    color: var(--color-text);
}

.difficulty-select:hover, .problem-count-input:hover {
    border-color: var(--color-primary-light);
}

.difficulty-select:focus, .problem-count-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.problem-count-input {
    width: 100px;
    text-align: center;
}

/* === Buttons === */
.btn {
    padding: var(--space-3) var(--space-6);
    font-size: 1.05em;
    font-weight: 700;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
    font-family: var(--font-family);
    box-shadow: var(--shadow-sm);
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn:active {
    transform: translateY(0);
    box-shadow: var(--shadow-sm);
}

.btn-generate {
    background: linear-gradient(135deg, var(--color-primary-light), var(--color-primary));
    color: white;
}

.btn-generate:hover {
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
}

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

.btn-check:hover {
    background: #059669;
}

.btn-hint {
    background: var(--color-warning-light);
    color: #92400e;
}

.btn-hint:hover {
    background: var(--color-warning);
    color: white;
}

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

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

/* === Problems Grid === */
.problems-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--space-6);
    margin: var(--space-6) 0;
}

/* === Problem Cards === */
.problem-container {
    position: relative;
    padding: var(--space-4);
    border-radius: var(--radius-lg);
    background: var(--color-surface);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    animation: fadeIn 0.3s ease;
    min-height: 200px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border: 1px solid var(--color-border);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

.problem-container:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

/* Animal shapes — subtle pastel backgrounds */
.animal-cat {
    background: #fef9c3;
    border-radius: 50% 50% var(--radius-lg) var(--radius-lg);
}

.animal-cat::before {
    content: "🐱";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-dog {
    background: #fce7f3;
    border-radius: 40% 60% 60% 40%;
}

.animal-dog::before {
    content: "🐶";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-bear {
    background: #f1f5f9;
    border-radius: 45%;
}

.animal-bear::before {
    content: "🐻";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-frog {
    background: #d1fae5;
    border-radius: 50% 50% 50% 50% / 60% 60% 40% 40%;
}

.animal-frog::before {
    content: "🐸";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-lion {
    background: #fef3c7;
    border-radius: 50%;
}

.animal-lion::before {
    content: "🦁";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-panda {
    background: #f8fafc;
    border-radius: 40%;
}

.animal-panda::before {
    content: "🐼";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-monkey {
    background: #fde68a;
    border-radius: 30% 70% 70% 30%;
}

.animal-monkey::before {
    content: "🐵";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

.animal-pig {
    background: #fce7f3;
    border-radius: 50% 50% 40% 40%;
}

.animal-pig::before {
    content: "🐷";
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 2.5em;
}

/* === Math Mountain Structure === */
.math-mountain {
    text-align: center;
    margin-top: var(--space-6);
    width: 100%;
}

.mountain-top {
    font-size: 1.8em;
    font-weight: 800;
    color: var(--color-text);
    margin-bottom: var(--space-3);
    padding: var(--space-3);
    background: rgba(99, 102, 241, 0.06);
    border-radius: var(--radius-md);
    border: 1.5px solid var(--color-primary-light);
}

.mountain-base {
    display: flex;
    justify-content: space-around;
    gap: var(--space-2);
    margin-top: var(--space-3);
}

.base-number {
    font-size: 1.6em;
    font-weight: 700;
    color: var(--color-text);
    padding: var(--space-3) var(--space-4);
    background: rgba(16, 185, 129, 0.06);
    border-radius: var(--radius-sm);
    border: 1.5px solid var(--color-success);
    flex: 1;
}

/* === Input Styling === */
.answer-input {
    width: 100%;
    min-width: 80px;
    padding: var(--space-3) var(--space-2);
    font-size: 1.4em;
    text-align: center;
    border: 1.5px solid var(--color-border);
    border-radius: 10px;
    margin-top: var(--space-2);
    font-family: var(--font-family);
    transition: var(--transition);
    box-sizing: border-box;
    color: var(--color-text);
    background: var(--color-surface);
}

.answer-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

/* === Correct / Incorrect States === */
.problem-container.correct {
    border-left: 4px solid var(--color-success);
    background: var(--color-success-light);
}

@keyframes celebrate {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.03); }
}

.problem-container.incorrect {
    border-left: 4px solid var(--color-error);
    background: var(--color-error-light);
    animation: shake 0.3s ease;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-4px); }
    75% { transform: translateX(4px); }
}

.status-icon {
    position: absolute;
    top: var(--space-2);
    right: var(--space-2);
    font-size: 1.8em;
}

/* === Results Section === */
.results-section {
    text-align: center;
    padding: var(--space-8);
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    margin-top: var(--space-6);
    color: var(--color-text);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
}

.results-section h2 {
    font-size: 2.2em;
    font-weight: 800;
    margin-bottom: var(--space-4);
    color: var(--color-primary);
}

.results-section.hidden {
    display: none;
}

#results-details {
    font-size: 1.3em;
    margin-top: var(--space-3);
    color: var(--color-text-muted);
}

/* === Tracing === */
.tracing-container {
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin: var(--space-4) 0;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border);
}

.tracing-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-4);
    padding-bottom: var(--space-4);
    border-bottom: 1px solid var(--color-border);
}

.current-letter {
    font-size: 3.5em;
    color: var(--color-primary);
    font-weight: 800;
    margin: 0;
}

.tracing-progress {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: var(--space-1);
    font-size: 1.1em;
    font-weight: 700;
    color: var(--color-text);
}

.tracing-picture {
    background: var(--color-warning-light);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin: var(--space-4) 0;
    text-align: center;
    animation: fadeIn 0.3s ease;
}

.picture-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-3);
}

.picture-emoji {
    font-size: 4em;
}

.picture-label {
    font-size: 1.8em;
    font-weight: 800;
    color: var(--color-text);
    text-transform: capitalize;
}

/* === Counting Area === */
.counting-area {
    background: linear-gradient(135deg, var(--color-primary-light), var(--color-primary));
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin: var(--space-4) 0;
    color: white;
}

.counting-instruction {
    font-size: 1.5em;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--space-4);
}

#count-target {
    color: #fde68a;
    font-size: 1.1em;
}

.counting-objects {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: var(--space-3);
    margin: var(--space-4) 0;
    justify-items: center;
}

.counting-object {
    font-size: 2.5em;
    cursor: pointer;
    transition: var(--transition);
    user-select: none;
}

.counting-object:hover {
    transform: scale(1.15);
}

.counting-object.counted {
    opacity: 0.3;
    transform: scale(0.8);
    filter: grayscale(100%);
}

.counting-result {
    text-align: center;
    font-size: 1.3em;
    font-weight: 700;
    margin-top: var(--space-4);
    min-height: 40px;
}

#counting-feedback {
    display: inline-block;
    padding: var(--space-2) var(--space-4);
    background: rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-full);
}

/* === Canvas === */
.canvas-wrapper {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-3);
    margin: var(--space-4) 0;
}

#tracing-canvas {
    border: 2px solid var(--color-primary-light);
    border-radius: var(--radius-md);
    background: white;
    cursor: crosshair;
    touch-action: none;
    box-shadow: var(--shadow-sm);
    max-width: 100%;
    height: auto;
}

.btn-clear-trace {
    padding: var(--space-3) var(--space-6);
    font-size: 1em;
    font-weight: 700;
    background: var(--color-error);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
    font-family: var(--font-family);
    box-shadow: var(--shadow-sm);
}

.btn-clear-trace:hover {
    background: #dc2626;
    box-shadow: var(--shadow-md);
}

/* === Tracing Feedback === */
.tracing-feedback {
    text-align: center;
    font-size: 1.3em;
    font-weight: 700;
    padding: var(--space-4);
    border-radius: var(--radius-md);
    margin-top: var(--space-4);
    min-height: 60px;
    animation: fadeIn 0.3s ease;
}

.tracing-feedback.excellent {
    background: var(--color-success-light);
    color: #065f46;
}

.tracing-feedback.good {
    background: rgba(99, 102, 241, 0.1);
    color: var(--color-primary-dark);
}

.tracing-feedback.needs-practice {
    background: var(--color-warning-light);
    color: #92400e;
}

body.dark-mode .tracing-feedback.excellent {
    background: rgba(16, 185, 129, 0.15);
    color: #6ee7b7;
}

body.dark-mode .tracing-feedback.good {
    background: rgba(99, 102, 241, 0.15);
    color: var(--color-primary-light);
}

body.dark-mode .tracing-feedback.needs-practice {
    background: rgba(245, 158, 11, 0.15);
    color: #fbbf24;
}

/* === Star Rating === */
.star-rating {
    display: flex;
    justify-content: center;
    gap: var(--space-4);
    margin-top: var(--space-4);
    padding: var(--space-4);
}

.star-rating.hidden {
    display: none !important;
}

.star {
    font-size: 3.5em;
    filter: grayscale(100%) brightness(0.5);
    transform: scale(0.5);
    transition: var(--transition);
    opacity: 0.3;
}

.star.earned {
    filter: grayscale(0%) brightness(1.1) drop-shadow(0 0 8px gold);
    transform: scale(1.1);
    opacity: 1;
    animation: starPop 0.5s ease;
}

@keyframes starPop {
    0% { transform: scale(0.5); opacity: 0; }
    60% { transform: scale(1.2); }
    100% { transform: scale(1.1); opacity: 1; }
}

.star.earned:nth-child(1) { animation-delay: 0s; }
.star.earned:nth-child(2) { animation-delay: 0.15s; }
.star.earned:nth-child(3) { animation-delay: 0.3s; }

/* === Word Problems === */
.word-problems-grid {
    display: flex;
    flex-direction: column;
    gap: var(--space-4);
    margin: var(--space-6) 0;
}

.word-problem-card {
    background: var(--color-surface);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border-left: 4px solid var(--color-primary);
    transition: var(--transition);
    animation: fadeIn 0.3s ease;
    border: 1px solid var(--color-border);
    border-left: 4px solid var(--color-primary);
}

.word-problem-card:hover {
    box-shadow: var(--shadow-md);
}

.word-problem-card h3 {
    color: var(--color-primary);
    font-size: 1.3em;
    font-weight: 700;
    margin-bottom: var(--space-3);
}

.word-problem-text {
    font-size: 1.15em;
    line-height: 1.7;
    color: var(--color-text);
    margin-bottom: var(--space-4);
    padding: var(--space-4);
    background: rgba(99, 102, 241, 0.04);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}

.word-problem-answer {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-size: 1.15em;
    font-weight: 600;
}

.word-problem-answer label {
    color: var(--color-text);
}

.word-problem-answer input {
    width: 140px;
    padding: var(--space-3);
    font-size: 1.1em;
    text-align: center;
    border: 1.5px solid var(--color-border);
    border-radius: 10px;
    font-family: var(--font-family);
    transition: var(--transition);
    color: var(--color-text);
    background: var(--color-surface);
}

.word-problem-answer input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.word-problem-card.correct {
    border-left-color: var(--color-success);
    background: var(--color-success-light);
}

.word-problem-card.incorrect {
    border-left-color: var(--color-error);
    background: var(--color-error-light);
    animation: shake 0.3s ease;
}

.word-problem-card .status-icon {
    position: absolute;
    top: var(--space-4);
    right: var(--space-4);
    font-size: 2em;
}

.word-problem-explanation {
    margin-top: var(--space-3);
    padding: var(--space-3);
    background: var(--color-border-light);
    border-radius: var(--radius-sm);
    font-size: 1em;
    color: var(--color-text);
    display: none;
}

.word-problem-card.checked .word-problem-explanation {
    display: block;
}

/* === Grade Cards (landing page) === */
.grade-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--space-6);
    padding: var(--space-6) 0;
}

.grade-card {
    background: var(--color-surface);
    border-radius: var(--radius-xl);
    padding: var(--space-8) var(--space-6);
    text-align: center;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    text-decoration: none;
    color: inherit;
    border: 2px solid var(--color-border);
    position: relative;
    overflow: hidden;
}

.grade-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-xl);
}

.grade-card-2 { border-color: var(--color-grade2); background: linear-gradient(135deg, #fff1f2 0%, #ffe4e6 100%); }
.grade-card-3 { border-color: var(--color-grade3); background: linear-gradient(135deg, #f0fdfa 0%, #ccfbf1 100%); }
.grade-card-4 { border-color: var(--color-grade4); background: linear-gradient(135deg, #fffbeb 0%, #fef3c7 100%); }
.grade-card-5 { border-color: var(--color-grade5); background: linear-gradient(135deg, #eef2ff 0%, #e0e7ff 100%); }

.grade-card:hover.grade-card-2 { border-color: #e11d48; }
.grade-card:hover.grade-card-3 { border-color: #0d9488; }
.grade-card:hover.grade-card-4 { border-color: #d97706; }
.grade-card:hover.grade-card-5 { border-color: var(--color-primary-dark); }

.grade-emoji { font-size: 3.5em; margin-bottom: var(--space-3); display: block; }
.grade-number { font-size: 1.8em; font-weight: 800; margin-bottom: var(--space-2); }

.grade-card-2 .grade-number { color: var(--color-grade2); }
.grade-card-3 .grade-number { color: var(--color-grade3); }
.grade-card-4 .grade-number { color: #b45309; }
.grade-card-5 .grade-number { color: var(--color-grade5); }

.grade-topics { list-style: none; padding: 0; margin: var(--space-3) 0 0; text-align: left; }
.grade-topics li { padding: var(--space-1) 0; font-size: 0.95em; color: var(--color-text-muted); }
.grade-topics li::before { content: '✨ '; }

body.dark-mode .grade-card {
    background: var(--color-surface);
    border-color: var(--color-border);
}

body.dark-mode .grade-card-2 { background: linear-gradient(135deg, #1c1217 0%, #2a1520 100%); border-color: #9f1239; }
body.dark-mode .grade-card-3 { background: linear-gradient(135deg, #0f1f1d 0%, #132a26 100%); border-color: #0d9488; }
body.dark-mode .grade-card-4 { background: linear-gradient(135deg, #1c1a0f 0%, #2a2513 100%); border-color: #b45309; }
body.dark-mode .grade-card-5 { background: linear-gradient(135deg, #151329 0%, #1e1b38 100%); border-color: var(--color-primary); }

body.dark-mode .grade-topics li { color: var(--color-text-muted); }

/* === Responsive === */
@media (max-width: 1200px) {
    .app-wrapper {
        flex-direction: column;
    }

    .history-sidebar {
        width: 100%;
        max-height: 280px;
        order: -1;
    }

    .counting-objects {
        grid-template-columns: repeat(3, 1fr);
    }

    .tab-navigation {
        display: flex;
        flex-wrap: nowrap;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }
}

@media (max-width: 768px) {
    body {
        padding: var(--space-2);
    }

    .container {
        padding: var(--space-4);
        border-radius: var(--radius-lg);
    }

    h1 {
        font-size: 1.8em;
    }

    .problems-grid {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
        gap: var(--space-3);
    }

    .controls-panel {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .tab-button {
        padding: var(--space-2) var(--space-3);
        font-size: 0.9em;
        white-space: nowrap;
    }

    .word-problem-text {
        font-size: 1em;
    }

    .history-sidebar {
        max-height: 220px;
    }

    .current-letter {
        font-size: 2.5em;
    }

    .picture-emoji {
        font-size: 3em;
    }

    .picture-label {
        font-size: 1.4em;
    }

    .counting-objects {
        grid-template-columns: repeat(2, 1fr);
    }

    .counting-object {
        font-size: 2em;
    }

    #tracing-canvas {
        width: 100%;
    }

    .grade-cards {
        grid-template-columns: 1fr;
    }
}

/* === Print === */
@media print {
    .history-sidebar,
    .btn,
    .controls-panel,
    .tab-navigation,
    button {
        display: none !important;
    }

    .app-wrapper {
        display: block;
    }

    .container {
        max-width: 100%;
        padding: var(--space-4);
        box-shadow: none;
        border: none;
    }

    .problems-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--space-4);
    }

    .problem-container {
        break-inside: avoid;
        page-break-inside: avoid;
    }

    body {
        background: white;
    }

    .answer-input {
        border: 2px solid #000;
        background: white;
    }
}

/* === Confetti === */
.confetti-particle {
    position: fixed;
    width: 8px;
    height: 8px;
    top: -10px;
    z-index: 10000;
    animation: confetti-fall linear forwards;
    pointer-events: none;
}

@keyframes confetti-fall {
    to {
        transform: translateY(100vh) rotate(720deg);
        opacity: 0;
    }
}

/* === Achievement Notification === */
.achievement-notification {
    position: fixed;
    top: -200px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--color-surface);
    padding: var(--space-6) var(--space-8);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    border: 2px solid var(--color-warning);
    z-index: 10000;
    transition: top 0.4s ease;
    max-width: 90%;
    text-align: center;
}

.achievement-notification.show {
    top: var(--space-4);
}

.achievement-content h3 {
    margin: 0 0 var(--space-2) 0;
    font-size: 1.5em;
    font-weight: 800;
    color: var(--color-text);
}

.achievement-content p {
    margin: var(--space-1) 0;
    color: var(--color-text-muted);
}

.achievement-content strong {
    font-size: 1.1em;
    color: var(--color-warning);
}

/* === Analytics Panel === */
.analytics-panel {
    background: rgba(99, 102, 241, 0.04);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin-top: var(--space-4);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border);
}

.analytics-panel.hidden {
    display: none;
}

.analytics-panel h3 {
    color: var(--color-primary);
    font-size: 1.5em;
    font-weight: 800;
    margin-bottom: var(--space-3);
}

.analytics-panel p {
    font-size: 1.1em;
    margin: var(--space-2) 0;
    color: var(--color-text);
}

.analytics-panel strong {
    color: var(--color-primary);
}

/* === Shortcut Hints === */
.shortcut-hint {
    font-size: 0.8em;
    color: var(--color-text-muted);
    margin-left: var(--space-1);
}

/* === Autosave Indicator === */
.autosave-indicator {
    position: fixed;
    bottom: var(--space-4);
    right: var(--space-4);
    background: var(--color-success);
    color: white;
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-full);
    font-size: 0.85em;
    font-weight: 600;
    z-index: 1000;
    animation: fadeInOut 2s ease;
}

@keyframes fadeInOut {
    0%, 100% { opacity: 0; }
    50% { opacity: 1; }
}

/* === Loading State (Bottom) === */
.loading {
    opacity: 0.6;
    pointer-events: none;
    position: relative;
}

.loading::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 32px;
    height: 32px;
    margin: -16px 0 0 -16px;
    border: 3px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}