:root {
    /* Color Palette - Premium Dark Theme */
    --bg-main: #0f172a;
    /* Slate 900 */
    --bg-panel: #1e293b;
    /* Slate 800 */
    --text-primary: #f1f5f9;
    /* Slate 100 */
    --text-secondary: #94a3b8;
    /* Slate 400 */
    --accent-primary: #38bdf8;
    /* Sky 400 */

    /* Function Colors */
    --color-sin: #f87171;
    /* Red 500 */
    --color-cos: #60a5fa;
    /* Blue 500 */
    --color-tan: #34d399;
    /* Emerald 500 */
    --color-cot: #ec4899;
    /* Pink 500 */
    --color-sec: #a855f7;
    /* Purple 500 */
    --color-csc: #f97316;
    /* Orange 500 */
    --color-angle: #fbbf24;
    /* Amber 400 */

    /* UI Elements */
    --border-color: #334155;
    /* Slate 700 */
    --shadow-soft: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-glow: 0 0 15px rgba(56, 189, 248, 0.15);
}

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

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-main);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-y: auto;
    /* 允許捲動以查看公式面板 */
    display: flex;
    justify-content: center;
}

.app-container {
    width: 100%;
    max-width: 1600px;
    height: 100%;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* Header */
.main-header {
    flex-shrink: 0;
    text-align: center;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}

.main-header h1 {
    font-weight: 700;
    font-size: 2rem;
    letter-spacing: -0.02em;
    background: linear-gradient(to right, var(--text-primary), var(--accent-primary));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Main Grid Layout */
.main-grid {
    flex: 1;
    display: grid;
    grid-template-columns: minmax(320px, .85fr) minmax(0, 1.6fr);
    /* Fixed sidebar, flexible content */
    gap: 20px;
    min-height: 0;
    /* Important for scroll calculations */
}

/* 公式面板橫跨整個 grid */
.main-grid>.formula-panel {
    grid-column: 1 / -1;
}

/* Right Column Container */
.right-column {
    display: flex;
    flex-direction: column;
    gap: 20px;
    height: 100%;
}

/* Panels */
.panel {
    background-color: var(--bg-panel);
    border-radius: 16px;
    padding: 20px;
    box-shadow: var(--shadow-soft);
    border: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

.panel-header {
    margin-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 10px;
}

.panel-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Info Panel Styles */
.info-panel {
    overflow-y: auto;
    align-self: start;
    /* Info panel naturally stretches in Grid */
}

.value-group {
    display: flex;
    flex-direction: column;
    gap: 20px;
    margin-bottom: 30px;
}

.value-item {
    background: rgba(15, 23, 42, 0.5);
    padding: 15px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 5px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.value-display {
    font-family: 'Roboto Mono', monospace;
    font-size: 1.2rem;
    /* Reduced from 1.5rem */
    font-weight: 500;
    color: var(--text-primary);
}

.info-note {
    background: rgba(56, 189, 248, 0.1);
    border-left: 4px solid var(--accent-primary);
    padding: 12px;
    margin-top: 5px;
    border-radius: 0 8px 8px 0;
}

.info-note p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.info-note p:last-child {
    margin-bottom: 0;
}

.math-font {
    font-family: 'Roboto Mono', monospace;
}

.divider {
    color: var(--border-color);
    margin: 0 10px;
}

/* Fraction Display Styles */
.frac-container {
    display: inline-flex;
    align-items: center;
    vertical-align: middle;
}

.frac {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    margin: 0 2px;
    font-size: 0.85em;
    /* Slightly smaller for fractions */
}

.num {
    border-bottom: 1px solid currentColor;
    padding: 0 2px;
    margin-bottom: 1px;
}

.den {
    padding: 0 2px;
}

/* Highlight Colors */
.highlight-sin {
    color: var(--color-sin);
}

.highlight-cos {
    color: var(--color-cos);
}

.highlight-tan {
    color: var(--color-tan);
}

/* Function Row Styling */
.func-row {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    font-size: 1.1rem;
    /* Allow wrapping if too long */
    gap: 0px;
    /* Removed gap as requested */
    /* Reduced from 1.4rem */
}

.func-label {
    font-weight: 600;
    margin-right: 2px;
    /* Tiny space between SIN and Angle */
}

.func-angle {
    color: var(--text-secondary);
    text-align: right;
}

.func-eq {
    color: var(--text-secondary);
    padding: 0 5px;
    /* Space around equals sign */
}

.func-identity {
    color: var(--text-secondary);
    font-size: 0.9em;
    /* Slightly smaller for the secondary identity */
}

.highlight-cos {
    color: var(--color-cos);
}

.highlight-tan {
    color: var(--color-tan);
}

.highlight-cot {
    color: var(--color-cot);
}

.highlight-sec {
    color: var(--color-sec);
}

.highlight-csc {
    color: var(--color-csc);
}

.highlight-angle {
    color: var(--color-angle);
}

/* Visualization Row (Circle + Controls) */
.visualization-row {
    display: flex;
    gap: 20px;
    min-height: 0;
    /* 由內容決定列高，避免控制面板與下方圖表重疊 */
    max-height: none;
}

/* Visualization Panel - takes remaining space in row */
.visualization-panel {
    position: relative;
    padding: 0;
    /* Let canvas fill */
    overflow: hidden;
    background: radial-gradient(circle at center, #1e293b 0%, #0f172a 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    flex: 1;
    min-height: 400px;
    height: 400px;
    align-self: flex-start;
    max-height: none;
}

/* New Controls Panel */
.controls-panel {
    width: 240px;
    /* Fixed width for controls */
    flex-shrink: 0;
    overflow: visible;
}

.canvas-container {
    width: 100%;
    height: 100%;
    position: relative;
}

canvas {
    display: block;
    width: 100%;
    height: 100%;
}

.overlay-instruction {
    position: absolute;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(0, 0, 0, 0.6);
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.8);
    pointer-events: none;
    opacity: 0.8;
}

/* Graph Panel (Bottom, now inside right column) */
.graph-panel {
    /* 圖表與說明採自然高度 */
    height: auto;
    flex-shrink: 0;
}

/* 公式面板樣式 Formula Panel Styles */
.formula-panel {
    margin-top: 20px;
    padding: 20px;
}

.formula-grid {
    display: grid;
    /* 使用 auto-fit 讓欄位自動適應 RWD，最小寬度 250px */
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 15px;
}

.formula-group {
    background: rgba(15, 23, 42, 0.5);
    padding: 15px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.formula-group h3 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent-primary);
    margin-bottom: 12px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border-color);
}

.formula {
    font-family: 'Roboto Mono', monospace;
    font-size: 0.9rem;
    color: var(--text-primary);
    margin-bottom: 8px;
    padding: 5px 0;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 4px;
}

.formula:last-child {
    margin-bottom: 0;
}

/* 公式面板內的分數樣式 */
.formula .frac {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    margin: 0 4px;
    font-size: 0.8em;
    vertical-align: middle;
}

.formula .frac .num {
    border-bottom: 1px solid var(--text-primary);
    padding: 0 4px 2px;
    margin-bottom: 2px;
}

.formula .frac .den {
    padding: 2px 4px 0;
}

/* 六邊形記憶法樣式 */
.hexagon-group {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.hexagon-svg {
    width: 180px;
    height: 180px;
    margin: 10px auto;
}

.hexagon-rules {
    width: 100%;
    margin-top: 10px;
}

.hexagon-rules .rule {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

/* Angle controls and readable identities */
.right-column, .panel { min-width: 0; }
.identity-row { color: var(--text-secondary); font-size: .85rem; margin-top: 10px; line-height: 1.7; }
.angle-controls { margin-bottom: 22px; }
.angle-controls h3 { font-size: 1rem; margin-bottom: 10px; }
.angle-controls label, .control-note, .graph-note, .formula-note { color: var(--text-secondary); font-size: .85rem; }
.angle-controls input[type="number"] { width: 100%; margin: 6px 0 10px; min-height: 42px; padding: 8px 10px; border: 1px solid var(--border-color); border-radius: 8px; background: var(--bg-main); color: var(--text-primary); font: inherit; }
.angle-controls input[type="range"] { width: 100%; accent-color: var(--accent-primary); min-height: 28px; }
.angle-presets { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; margin: 10px 0; }
.angle-presets button, #reset-angle { min-height: 40px; border: 1px solid var(--border-color); border-radius: 7px; background: var(--bg-main); color: var(--text-primary); font: inherit; font-size: .85rem; cursor: pointer; }
.angle-presets button:hover, #reset-angle:hover { background: #0c4a6e; border-color: var(--accent-primary); }
#reset-angle { width: 100%; margin-bottom: 8px; }
input:focus-visible, button:focus-visible, canvas:focus-visible, a:focus-visible { outline: 3px solid var(--accent-primary); outline-offset: 3px; }
#unit-circle-canvas { touch-action: none; cursor: crosshair; }
#unit-circle-canvas:active { cursor: grabbing; }
.graph-note { margin-bottom: 12px; }
.graph-panel .wide { height: 280px; flex: none; }
.formula-note { margin-bottom: 14px; }
.overlay-instruction { white-space: nowrap; padding: 6px 12px; bottom: 10px; font-size: .75rem; }
@media (max-width: 1150px) {
    .main-grid { grid-template-columns: minmax(0, 1fr); }
    .right-column { height: auto; }
    .value-group { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-bottom: 15px; }
    .info-panel { overflow: visible; }
    .visualization-row { height: auto; max-height: none; align-items: flex-start; }
    .formula-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 700px) {
    .visualization-row { flex-direction: column; }
    .visualization-panel, .controls-panel { width: 100%; flex: none; }
    .value-group, .formula-grid { grid-template-columns: minmax(0, 1fr); }
}