:root {
    --bg-color: #0c0e12;
    --card-bg: rgba(255, 255, 255, 0.03);
    --glass-bg: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-hover: rgba(255, 255, 255, 0.08);
    --text-main: #f8f9fa;
    --text-sub: #94a3b8;
    --accent-1: #6366f1; /* Indigo */
    --accent-2: #ec4899; /* Pink */
    --accent-3: #10b981; /* Emerald */
    --accent-4: #f59e0b; /* Amber */
    --accent-blue: #3b82f6; /* Blue */
    --accent-orange: #f97316; /* Orange */
}

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

body {
    font-family: 'Outfit', 'Helvetica Neue', Arial, 'Hiragino Kaku Gothic ProN', Meiryo, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    overflow-x: hidden;
    position: relative;
    padding: 2rem 1rem;
}

/* Background blob decorations */
.background-decor {
    position: absolute;
    width: 400px;
    height: 400px;
    border-radius: 50%;
    filter: blur(120px);
    z-index: 0;
    opacity: 0.15;
    pointer-events: none;
}

.blob-1 {
    background: var(--accent-1);
    top: 10%;
    left: 10%;
}

.blob-2 {
    background: var(--accent-2);
    bottom: 10%;
    right: 10%;
}

.container {
    width: 100%;
    max-width: 1100px;
    z-index: 1;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

header {
    text-align: center;
    margin-bottom: 0.5rem;
}

header h1 {
    font-size: 2.2rem;
    font-weight: 800;
    letter-spacing: -1px;
    margin-bottom: 0.5rem;
}

header h1 span {
    background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

header p {
    font-size: 0.95rem;
    color: var(--text-sub);
}

/* Main Navigation Tabs Wrapper & Indicator */
.nav-tabs-wrapper {
    position: relative;
    width: 100%;
}

.nav-tabs {
    display: flex;
    justify-content: flex-start;
    flex-wrap: nowrap;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin; /* Firefox */
    scrollbar-color: rgba(255, 255, 255, 0.2) transparent; /* Firefox */
    gap: 0.5rem;
    background: var(--card-bg);
    border: 1px solid var(--glass-border);
    padding: 0.4rem 2.5rem 0.6rem 0.4rem; /* Reserve space for scroll indicator */
    border-radius: 12px;
}

.nav-scroll-indicator {
    position: absolute;
    right: 2px;
    top: 50%;
    transform: translateY(-50%);
    width: 45px;
    height: calc(100% - 4px);
    background: linear-gradient(to right, rgba(15, 23, 42, 0) 0%, rgba(15, 23, 42, 0.85) 60%);
    color: var(--accent-orange);
    display: flex;
    align-items: center;
    justify-content: flex-end;
    padding-right: 12px;
    font-size: 1.2rem;
    font-weight: bold;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.3s ease;
    border-radius: 0 10px 10px 0;
    animation: pulseArrow 1.5s infinite;
}

@keyframes pulseArrow {
    0%, 100% { transform: translateY(-50%) translateX(0); }
    50% { transform: translateY(-50%) translateX(3px); }
}

.nav-tabs::-webkit-scrollbar {
    height: 4px; /* Thin scrollbar for Webkit */
    display: block;
}

.nav-tabs::-webkit-scrollbar-track {
    background: transparent;
}

.nav-tabs::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.15);
    border-radius: 10px;
}

.nav-tabs::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.3);
}

.tab-btn {
    background: transparent;
    border: none;
    color: var(--text-sub);
    padding: 0.6rem 1.2rem;
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    white-space: nowrap; /* Prevent wrapping inside buttons */
}

.tab-btn:hover {
    color: var(--text-main);
    background: var(--glass-hover);
}

.tab-btn.active {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* Tab contents */
.tab-content {
    display: none;
}

.tab-content.active {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 1.5rem;
}

@media (max-width: 900px) {
    .tab-content.active {
        grid-template-columns: 1fr;
    }
}

/* Layout Elements */
.canvas-panel {
    background: var(--card-bg);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    padding: 1rem;
    position: relative;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 480px;
    backdrop-filter: blur(10px);
}

.control-panel {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    backdrop-filter: blur(10px);
}

/* SVGs & Canvas Styles */
svg.visualizer-svg {
    width: 100%;
    height: auto;
    aspect-ratio: 5 / 4;
    background: rgba(0, 0, 0, 0.15);
    border-radius: 12px;
    overflow: visible;
    user-select: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -webkit-touch-callout: none;
    touch-action: none;
}

svg.visualizer-svg * {
    user-select: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -webkit-touch-callout: none;
}

.drag-handle {
    cursor: move;
    fill: #ffffff;
    stroke: var(--accent-1);
    stroke-width: 3px;
    transition: transform 0.1s ease, fill 0.2s ease;
    transform-origin: center;
    transform-box: fill-box;
}

.drag-handle:hover {
    fill: var(--accent-2);
    transform: scale(1.2);
}

/* Control UI Elements */
.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.control-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-sub);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.control-label span.val {
    color: var(--text-main);
    font-family: monospace;
    font-size: 0.95rem;
}

/* Sliders */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: rgba(255, 255, 255, 0.1);
    outline: none;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--accent-1);
    cursor: pointer;
    transition: transform 0.1s;
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.2);
}

/* Custom Buttons */
.btn-primary {
    background: linear-gradient(135deg, var(--accent-1), var(--accent-blue));
    color: white;
    border: none;
    padding: 0.75rem 1.2rem;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    font-family: inherit;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 0.6rem 1rem;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    font-family: inherit;
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1);
}

/* Radio Group */
.radio-group {
    display: flex;
    gap: 0.5rem;
    background: rgba(0, 0, 0, 0.2);
    padding: 0.25rem;
    border-radius: 8px;
    border: 1px solid var(--glass-border);
}

.radio-btn {
    flex: 1;
    text-align: center;
}

.radio-btn input {
    display: none;
}

.radio-btn label {
    display: block;
    padding: 0.5rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-sub);
    transition: all 0.2s;
}

.radio-btn input:checked + label {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-main);
}

/* Explanation & Text Box */
.explanation-card {
    background: rgba(255, 255, 255, 0.01);
    border-left: 4px solid var(--accent-1);
    padding: 1rem;
    border-radius: 0 8px 8px 0;
    font-size: 0.9rem;
    line-height: 1.5;
    color: var(--text-sub);
}

.explanation-card strong {
    color: var(--text-main);
    display: block;
    margin-bottom: 0.25rem;
}

.formula-display {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 0.75rem;
    font-family: 'Outfit', sans-serif;
    font-size: 1rem;
    text-align: center;
    color: var(--text-main);
}

/* Specific Visualization Classes */
.triangle-pyramid-a {
    fill: rgba(99, 102, 241, 0.15);
    stroke: var(--accent-1);
    stroke-width: 2;
}

.triangle-pyramid-b {
    fill: rgba(236, 72, 153, 0.1);
    stroke: var(--accent-2);
    stroke-width: 2;
    stroke-dasharray: 4 2;
}

.ratio-label {
    font-size: 0.85rem;
    font-weight: bold;
    fill: #ffffff;
    text-shadow: 0 1px 4px rgba(0,0,0,0.8);
    pointer-events: none;
}

/* Angle symbols */
.angle-arc {
    fill: none;
    stroke-width: 2;
}

/* Legend colors */
.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
}

.legend-color {
    width: 12px;
    height: 12px;
    border-radius: 3px;
}

/* Hint Banner */
.drag-hint {
    position: absolute;
    top: 1rem;
    left: 1rem;
    background: rgba(0,0,0,0.6);
    border: 1px solid var(--glass-border);
    padding: 0.4rem 0.8rem;
    border-radius: 20px;
    font-size: 0.75rem;
    pointer-events: none;
    display: flex;
    align-items: center;
    gap: 0.4rem;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 0.8; }
    50% { opacity: 0.4; }
}

/* Canvas Floating Play Button */
.canvas-play-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    width: 42px;
    height: 42px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.15);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: white;
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background 0.2s, transform 0.2s, box-shadow 0.2s;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.25);
    z-index: 10;
}

.canvas-play-btn:hover {
    background: var(--accent-1);
    transform: scale(1.1);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
    border-color: rgba(255, 255, 255, 0.3);
}

.canvas-play-btn:active {
    transform: scale(0.95);
}

/* Responsive adjustments for mobile viewports */
@media (max-width: 600px) {
    .drag-hint {
        top: auto;
        bottom: 1rem; /* スマホ画面では重なりを防ぐため左下に移動 */
        left: 1rem;
        font-size: 0.7rem;
        padding: 0.3rem 0.6rem;
    }
    
    .canvas-play-btn {
        width: 38px;
        height: 38px;
        font-size: 1.0rem;
        top: 0.8rem;
        right: 0.8rem;
    }
}