/* =============================================
   TRACKBEES CALCULATOR SUITE — Modern Light Theme
   ============================================= */

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

/* ---------- CSS Variables ---------- */
:root {
    --bg: #f0f2f8;
    --surface: #ffffff;
    --surface-hover: #f8f9fc;
    --text: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --accent: #6366f1;
    --accent-light: #818cf8;
    --accent-dark: #4f46e5;
    --accent-gradient: linear-gradient(135deg, #6366f1, #8b5cf6);
    --accent-glow: rgba(99, 102, 241, 0.15);
    --border: #e2e8f0;
    --border-hover: #cbd5e1;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.04), 0 1px 2px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.05), 0 2px 4px -2px rgba(0,0,0,0.05);
    --shadow-lg: 0 10px 25px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);
    --shadow-xl: 0 20px 40px -4px rgba(0,0,0,0.1);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --sidebar-width: 260px;
    --danger: #ef4444;
    --danger-hover: #dc2626;
    --success: #22c55e;
    --warning: #f59e0b;
    --ai-color: #8b5cf6;
    --ai-hover: #7c3aed;
}

/* ---------- Dark Theme Override ---------- */
[data-theme="dark"] {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface-hover: #273548;
    --text: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border: #334155;
    --border-hover: #475569;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.2);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.25);
    --shadow-lg: 0 10px 25px rgba(0,0,0,0.3);
    --shadow-xl: 0 20px 40px rgba(0,0,0,0.4);
    --accent-glow: rgba(99, 102, 241, 0.25);
}

/* ---------- Reset & Base ---------- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ---------- Container Layout ---------- */
.container {
    display: flex;
    min-height: 100vh;
    width: 100%;
}

/* ---------- Sidebar ---------- */
.sidebar {
    width: var(--sidebar-width);
    background: var(--surface);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    height: 100vh;
    position: fixed;
    left: 0;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-md);
    transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

.sidebar-header {
    padding: 1.25rem 1.25rem 1rem;
    border-bottom: 1px solid var(--border);
    text-align: center;
}

.sidebar-header img {
    max-width: 120px;
    height: auto;
    margin-bottom: 0.5rem;
}

.sidebar-header h2 {
    margin: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--accent);
}

.nav-buttons {
    padding: 0.75rem;
    display: flex;
    flex-direction: column;
    gap: 4px;
    flex: 1;
    overflow-y: auto;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.7rem 1rem;
    border-radius: var(--radius-sm);
    color: var(--text);
    text-decoration: none;
    transition: var(--transition);
    position: relative;
}

.nav-btn i {
    font-size: 1.1rem;
    width: 24px;
    text-align: center;
    color: var(--text-secondary);
    transition: var(--transition);
}

.nav-text {
    font-size: 0.9rem;
    font-weight: 500;
}

.nav-description {
    display: none;
}

.nav-btn:hover {
    background: var(--accent-glow);
    transform: translateX(3px);
}

.nav-btn:hover i {
    color: var(--accent);
}

.nav-btn.active {
    background: var(--accent-gradient);
    color: #ffffff;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.nav-btn.active i {
    color: #ffffff;
}

.nav-btn.active .nav-text {
    color: #ffffff;
}

.sidebar-footer {
    padding: 0.75rem;
    border-top: 1px solid var(--border);
}

.theme-btn {
    width: 100%;
    padding: 0.7rem;
    border-radius: var(--radius-sm);
    background: var(--surface-hover);
    color: var(--text);
    border: 1px solid var(--border);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: var(--transition);
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 500;
}

.theme-btn:hover {
    background: var(--accent-glow);
    border-color: var(--accent);
    color: var(--accent);
}

/* ---------- Mobile Hamburger ---------- */
.mobile-toggle {
    display: none;
    position: fixed;
    top: 1rem;
    left: 1rem;
    z-index: 200;
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    background: var(--surface);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-md);
    cursor: pointer;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    color: var(--text);
    transition: var(--transition);
}

.mobile-toggle:hover {
    background: var(--accent-glow);
    border-color: var(--accent);
    color: var(--accent);
}

.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.3);
    backdrop-filter: blur(4px);
    z-index: 90;
}

.sidebar-overlay.active {
    display: block;
}

/* ---------- Main Content ---------- */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-left: var(--sidebar-width);
    padding: 1.5rem;
    min-height: 100vh;
    transition: margin-left 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---------- Buttons ---------- */
.btn {
    padding: 0.65rem 1.25rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    white-space: nowrap;
}

.btn:hover {
    background: var(--surface-hover);
    border-color: var(--border-hover);
    box-shadow: var(--shadow-sm);
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(0);
}

.btn.primary {
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    box-shadow: 0 2px 8px rgba(99, 102, 241, 0.25);
}

.btn.primary:hover {
    box-shadow: 0 4px 16px rgba(99, 102, 241, 0.35);
    transform: translateY(-2px);
}

.btn.danger {
    background: var(--danger);
    color: #ffffff;
    border-color: var(--danger);
}

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

.btn.ai {
    background: linear-gradient(135deg, #8b5cf6, #a855f7);
    color: #ffffff;
    border: none;
    box-shadow: 0 2px 8px rgba(139, 92, 246, 0.25);
}

.btn.ai:hover {
    box-shadow: 0 4px 16px rgba(139, 92, 246, 0.35);
    transform: translateY(-2px);
}

.btn.theme {
    background: var(--surface-hover);
    color: var(--text);
    border: 1px solid var(--border);
}

.btn.theme:hover {
    background: var(--accent-glow);
    border-color: var(--accent);
    color: var(--accent);
}

/* ---------- Form Inputs ---------- */
.form-input,
input[type="text"],
input[type="number"] {
    font-family: inherit;
    padding: 0.65rem 0.9rem;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-size: 0.95rem;
    transition: var(--transition);
    outline: none;
}

.form-input:focus,
input[type="text"]:focus,
input[type="number"]:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

input[type="color"] {
    width: 44px;
    height: 44px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    padding: 2px;
    background: var(--surface);
    transition: var(--transition);
}

input[type="color"]:hover {
    border-color: var(--accent);
}

input[type="range"] {
    accent-color: var(--accent);
    width: 130px;
}

/* ---------- Notifications ---------- */
.notification {
    position: fixed;
    top: 1.25rem;
    right: 1.25rem;
    padding: 0.85rem 1.25rem;
    background: var(--surface);
    color: var(--text);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    border-left: 4px solid var(--accent);
    animation: slideInRight 0.35s ease-out;
}

.notification.success {
    border-left-color: var(--success);
}

.notification.success i { color: var(--success); }

.notification.error {
    border-left-color: var(--danger);
}

.notification.error i { color: var(--danger); }

@keyframes slideInRight {
    from { opacity: 0; transform: translateX(30px); }
    to   { opacity: 1; transform: translateX(0); }
}

/* =============================================
   HOME PAGE — Index
   ============================================= */
.welcome-section {
    text-align: center;
    padding: 2.5rem 1rem 1.5rem;
}

.logo-container {
    margin-bottom: 1rem;
}

.logo-container img {
    max-width: 160px;
    height: auto;
    filter: drop-shadow(0 4px 12px rgba(99, 102, 241, 0.15));
}

.main-title {
    font-size: 2rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.05rem;
    font-weight: 400;
}

.calculator-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.25rem;
    padding: 1rem 1.5rem 2rem;
}

.calculator-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 2rem 1.5rem;
    text-align: center;
    cursor: pointer;
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    animation: cardEntrance 0.5s ease-out both;
}

.calculator-card:nth-child(1) { animation-delay: 0.05s; }
.calculator-card:nth-child(2) { animation-delay: 0.10s; }
.calculator-card:nth-child(3) { animation-delay: 0.15s; }
.calculator-card:nth-child(4) { animation-delay: 0.20s; }
.calculator-card:nth-child(5) { animation-delay: 0.25s; }

.calculator-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-xl);
    border-color: var(--accent-light);
}

.card-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    width: 64px;
    height: 64px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-md);
    background: var(--accent-glow);
    color: var(--accent);
}

.card-title {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text);
}

.card-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.5;
}

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

/* =============================================
   SCIENTIFIC CALCULATOR
   ============================================= */
.calculator-display {
    background: var(--surface);
    padding: 1rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.calc-display {
    width: 100%;
    padding: 1rem 1.25rem;
    font-size: 1.75rem;
    font-weight: 500;
    background: var(--bg);
    color: var(--text);
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    text-align: right;
    font-family: 'Inter', monospace;
    transition: var(--transition);
}

.calc-display:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.calculator-pad {
    background: var(--surface);
    padding: 1rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.calculator-pad .function-buttons {
    display: flex;
    gap: 0.4rem;
    flex-wrap: wrap;
}

.calculator-pad .function-buttons .btn {
    flex: 1;
    min-width: 50px;
    justify-content: center;
    font-size: 0.85rem;
    padding: 0.6rem;
    background: var(--accent-glow);
    color: var(--accent);
    border: 1px solid transparent;
    font-weight: 600;
}

.calculator-pad .function-buttons .btn:hover {
    background: var(--accent);
    color: #ffffff;
}

.number-pad {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.4rem;
    margin-top: 0.5rem;
}

.number-pad .btn {
    padding: 1.1rem;
    font-size: 1.15rem;
    font-weight: 600;
    justify-content: center;
    border-radius: var(--radius-sm);
    background: var(--surface-hover);
    border: 1px solid var(--border);
}

.number-pad .btn:hover {
    background: var(--accent-glow);
    border-color: var(--accent-light);
    color: var(--accent);
}

.btn.equals {
    grid-column: 1 / -1;
    margin-top: 0.3rem;
    padding: 1rem;
    font-size: 1.25rem;
}

/* =============================================
   GRAPHING CALCULATOR
   ============================================= */
.graph-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.graph-tab {
    padding: 0.6rem 1.25rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.graph-tab:hover {
    background: var(--accent-glow);
    border-color: var(--accent-light);
}

.graph-tab.active {
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    box-shadow: 0 2px 8px rgba(99, 102, 241, 0.25);
}

.graph-controls {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    margin-bottom: 1rem;
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.graph-controls .function-buttons {
    display: flex;
    gap: 0.4rem;
    margin-top: 0.5rem;
    flex-wrap: wrap;
}

.graph-controls .function-buttons button {
    padding: 0.45rem 0.85rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-hover);
    color: var(--text);
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 500;
}

.graph-controls .function-buttons button:hover {
    background: var(--accent-glow);
    border-color: var(--accent);
    color: var(--accent);
}

.range-controls {
    display: flex;
    gap: 1.25rem;
    margin: 1rem 0;
    flex-wrap: wrap;
}

.range-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.range-group label {
    font-weight: 600;
    color: var(--text);
}

.range-group input[type="number"] {
    width: 70px;
    padding: 0.4rem 0.5rem;
    text-align: center;
    font-size: 0.85rem;
}

.graph-container {
    background: var(--surface);
    padding: 0.75rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
    height: calc(100vh - 280px);
    min-height: 350px;
}

#graph, #loveGraphPlot {
    width: 100%;
    height: 100%;
}

/* =============================================
   MATRIX CALCULATOR
   ============================================= */
.matrix-container {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    padding: 0.25rem;
}

.matrix-input-group {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.matrix-input-group:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--border-hover);
}

.matrix-input-group h3 {
    color: var(--accent);
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.matrix-input-group h3::before {
    content: '⊞';
    font-size: 1.1em;
}

.matrix-controls {
    display: flex;
    gap: 0.75rem;
    align-items: center;
    margin-bottom: 1rem;
    padding: 0.75rem;
    background: var(--bg);
    border-radius: var(--radius-sm);
}

.dimension-controls {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.dimension-input {
    width: 60px;
    padding: 0.55rem;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-family: inherit;
    font-size: 1rem;
    text-align: center;
    transition: var(--transition);
}

.dimension-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
    outline: none;
}

.matrix-grid {
    display: grid;
    gap: 0.5rem;
    padding: 1rem;
    background: var(--bg);
    border-radius: var(--radius-sm);
    margin-top: 0.5rem;
}

.matrix-input {
    width: 100%;
    padding: 0.6rem;
    text-align: center;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-family: inherit;
    font-size: 1rem;
    transition: var(--transition);
}

.matrix-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
    outline: none;
}

.matrix-input:read-only {
    background: var(--accent-glow);
    border-color: var(--accent-light);
    font-weight: 600;
    color: var(--accent-dark);
}

.matrix-operations {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.matrix-operations .btn {
    min-width: 130px;
    justify-content: center;
    font-weight: 500;
}

.matrix-operations .btn i {
    margin-right: 0.25rem;
}

.matrix-result {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.matrix-result h3 {
    color: var(--accent);
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.matrix-result h3::before {
    content: '=';
    font-size: 1.1em;
    font-weight: 700;
}

/* =============================================
   UNIT CONVERTER
   ============================================= */
.converter-container {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    max-width: 750px;
    margin: 0 auto;
    width: 100%;
}

.converter-tabs {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.converter-tab {
    padding: 0.7rem 1.5rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 500;
}

.converter-tab:hover {
    background: var(--accent-glow);
    border-color: var(--accent-light);
}

.converter-tab.active {
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    box-shadow: 0 2px 8px rgba(99, 102, 241, 0.25);
}

.converter-input-group {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    padding: 1.5rem;
    background: var(--surface);
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.input-section, .output-section {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.converter-input {
    width: 100%;
    padding: 0.85rem 1rem;
    font-size: 1.1rem;
    font-family: inherit;
    background: var(--bg);
    color: var(--text);
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.converter-input:focus {
    border-color: var(--accent);
    outline: none;
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.unit-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.converter-arrow {
    font-size: 1.5rem;
    color: var(--accent);
    flex-shrink: 0;
    animation: pulseArrow 2s ease-in-out infinite;
}

.convert-btn {
    align-self: center;
    min-width: 180px;
    justify-content: center;
    font-size: 1rem;
    padding: 0.8rem 2rem;
}

.conversion-history {
    background: var(--surface);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
}

.conversion-history h3 {
    color: var(--text);
    margin-bottom: 0.75rem;
    font-size: 1rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.conversion-history h3 i {
    color: var(--accent);
}

.history-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.65rem 0.5rem;
    border-bottom: 1px solid var(--border);
    font-size: 0.9rem;
    animation: fadeIn 0.3s ease;
}

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

.history-item i {
    color: var(--accent);
    font-size: 0.8rem;
}

@keyframes pulseArrow {
    0%, 100% { transform: scale(1); opacity: 0.7; }
    50%      { transform: scale(1.15); opacity: 1; }
}

/* =============================================
   DRAWING BOARD
   ============================================= */
.tools {
    background: var(--surface);
    padding: 0.85rem 1rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    display: flex;
    gap: 1.25rem;
    align-items: center;
    flex-wrap: wrap;
}

.tool-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.tool-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
}

#brushSizeValue {
    min-width: 40px;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.8rem;
    font-weight: 500;
}

.canvas-container {
    flex: 1;
    background: var(--surface);
    padding: 0.35rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    overflow: hidden;
    position: relative;
    min-height: 300px;
}

#drawingCanvas {
    width: 100%;
    height: 100%;
    background: #ffffff;
    cursor: crosshair;
    display: block;
    border-radius: calc(var(--radius-md) - 4px);
}

[data-theme="dark"] #drawingCanvas {
    background: #1e293b;
}

.button-group {
    display: flex;
    gap: 0.4rem;
    margin-left: auto;
}

.preview-panel {
    width: 220px;
    background: var(--surface);
    border-radius: var(--radius-md);
    padding: 1rem;
    border: 1px solid var(--border);
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
    max-height: 100vh;
    flex-shrink: 0;
}

.preview-panel h3 {
    margin: 0 0 0.5rem;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text);
    border-bottom: 1px solid var(--border);
    padding-bottom: 0.5rem;
}

#drawings-container {
    overflow-y: auto;
    flex: 1;
    padding-right: 0.25rem;
    scroll-behavior: smooth;
}

#drawings-container::-webkit-scrollbar { width: 4px; }
#drawings-container::-webkit-scrollbar-track { background: transparent; }
#drawings-container::-webkit-scrollbar-thumb {
    background-color: var(--border);
    border-radius: 4px;
}

.drawing-preview {
    margin-bottom: 0.75rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    transition: var(--transition);
}

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

.drawing-preview img {
    width: 100%;
    display: block;
}

.preview-time {
    padding: 0.35rem 0.5rem;
    background: var(--bg);
    color: var(--text-secondary);
    font-size: 0.7rem;
    text-align: center;
    font-weight: 500;
}

/* ---------- AI Result Box ---------- */
.ai-result-box {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--surface);
    border-top: 2px solid var(--ai-color);
    padding: 1.25rem;
    transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 1000;
    max-height: 35vh;
    overflow-y: auto;
    box-shadow: 0 -4px 20px rgba(0,0,0,0.1);
}

.ai-result-box.hidden {
    transform: translateY(100%);
}

.ai-result-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.ai-result-header h3 {
    margin: 0;
    color: var(--ai-color);
    font-size: 1rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-close {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.35rem;
    font-size: 1.1rem;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.btn-close:hover {
    background: var(--bg);
    color: var(--text);
}

.ai-result-content {
    font-family: 'Inter', monospace;
    font-size: 0.9rem;
    white-space: pre-wrap;
    padding: 1rem;
    background: var(--bg);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    line-height: 1.7;
}

/* =============================================
   RESPONSIVE — Tablet
   ============================================= */
@media (max-width: 900px) {
    .converter-input-group {
        flex-direction: column;
        gap: 1rem;
    }

    .preview-panel {
        display: none;
    }

    .range-controls {
        flex-direction: column;
        gap: 0.75rem;
    }
}

/* =============================================
   RESPONSIVE — Mobile
   ============================================= */
@media (max-width: 768px) {
    .mobile-toggle {
        display: flex;
    }

    .sidebar {
        transform: translateX(-100%);
        width: 260px;
        box-shadow: var(--shadow-xl);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .main-content {
        margin-left: 0;
        padding: 4.5rem 1rem 1rem;
    }

    /* Home page */
    .welcome-section {
        padding: 1rem 0.5rem;
    }

    .main-title {
        font-size: 1.5rem;
    }

    .calculator-grid {
        grid-template-columns: 1fr;
        padding: 0.75rem;
        gap: 0.75rem;
    }

    .calculator-card {
        padding: 1.25rem 1rem;
    }

    .card-icon {
        width: 52px;
        height: 52px;
        font-size: 1.8rem;
    }

    /* Drawing tools */
    .tools {
        flex-direction: column;
        gap: 0.75rem;
        align-items: stretch;
    }

    .tool-group {
        justify-content: center;
    }

    .button-group {
        margin-left: 0;
        justify-content: center;
        flex-wrap: wrap;
    }

    /* Calculator */
    .calc-display {
        font-size: 1.35rem;
        padding: 0.75rem;
    }

    .number-pad .btn {
        padding: 0.85rem;
        font-size: 1rem;
    }

    .calculator-pad .function-buttons .btn {
        padding: 0.5rem;
        font-size: 0.8rem;
    }

    /* Converter */
    .converter-tabs { flex-direction: column; }
    .converter-tab { justify-content: center; }

    /* Matrix */
    .matrix-controls {
        flex-direction: column;
        align-items: stretch;
    }

    .dimension-controls {
        justify-content: center;
    }

    .matrix-operations {
        justify-content: center;
    }

    .matrix-operations .btn {
        min-width: calc(50% - 0.5rem);
        font-size: 0.85rem;
    }

    /* Graphing */
    .graph-tabs {
        flex-direction: column;
    }

    .graph-container {
        height: calc(100vh - 320px);
        min-height: 280px;
    }

    .graph-controls .function-buttons button {
        flex: 1;
        min-width: 0;
        text-align: center;
    }
}

/* =============================================
   ANIMATIONS
   ============================================= */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-8px); }
    to   { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
    0%   { transform: scale(1); }
    50%  { transform: scale(1.05); }
    100% { transform: scale(1); }
}

/* ---------- Smooth Scrollbar ---------- */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* ---------- Selection Color ---------- */
::selection {
    background: var(--accent-glow);
    color: var(--accent-dark);
}