:root {
    --bg-top: #0a0a0a;
    --bg-bottom: #1a1a1a;
    --panel-bg: rgba(20, 24, 36, 0.85);
    --panel-border: rgba(255, 255, 255, 0.1);
    --text-main: #f0f4ff;
    --text-muted: rgba(240,244,255,0.7);
    --accent: #ff9d5c;
    --accent-hover: #ffb37a;
    --font-sans: "Source Han Sans", "Noto Sans SC", "Helvetica Neue", Arial, sans-serif;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: var(--font-sans);
    color: var(--text-main);
    background: linear-gradient(var(--bg-top), var(--bg-bottom));
    overflow: hidden;
}

#scene-canvas {
    position: fixed;
    inset: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
}

.sidebar {
    position: absolute;
    top: 40px;
    left: 40px;
    width: min(400px, 90vw);
    background: var(--panel-bg);
    border: 1px solid var(--panel-border);
    border-radius: 16px;
    padding: 24px;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    box-shadow: 0 20px 50px rgba(0,0,0,0.5);
    display: flex;
    flex-direction: column;
    gap: 24px;
    z-index: 100; /* Ensure high z-index */
    max-height: calc(100vh - 80px);
    overflow-y: auto;
    pointer-events: auto; /* Ensure clicks are registered */
    transition: transform 0.3s cubic-bezier(0.4, 0.0, 0.2, 1);
}

/* Toggle Button (Mobile Only by default) */
.sidebar-toggle {
    display: none; /* Hidden on desktop */
    position: absolute;
    top: 10px;
    right: 10px;
    width: 30px;
    height: 30px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    z-index: 20;
}

.sidebar-toggle::after {
    content: '';
    display: block;
    width: 10px;
    height: 10px;
    border-right: 2px solid white;
    border-bottom: 2px solid white;
    transform: rotate(45deg);
    margin-top: -4px;
    transition: transform 0.3s;
}

.sidebar.collapsed .sidebar-toggle::after {
    transform: rotate(-135deg);
    margin-top: 4px;
}

.lang-switcher {
    display: flex;
    gap: 8px;
    margin-bottom: 8px;
}

.lang-btn {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    padding: 4px 10px;
    font-size: 0.8rem;
    color: var(--text-muted);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s;
}

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

.lang-btn.active {
    background: var(--accent);
    color: #1a0f00;
    border-color: var(--accent);
    font-weight: 600;
}

.eyebrow {
    font-size: 0.75rem;
    letter-spacing: 0.2em;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 8px;
}

h1 {
    margin: 0 0 12px;
    font-size: 1.6rem;
    font-weight: 600;
    line-height: 1.2;
}

.intro {
    color: var(--text-muted);
    line-height: 1.6;
    font-size: 0.95rem;
    margin: 0;
}

.controls {
    display: flex;
    flex-direction: column;
    gap: 16px;
    padding-top: 16px;
    border-top: 1px solid var(--panel-border);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.control-group label {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-weight: 500;
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    cursor: pointer;
}

/* Button Group for Modes */
.mode-selector {
    display: flex;
    gap: 8px;
}

.mode-btn {
    flex: 1;
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--panel-border);
    color: var(--text-muted);
    padding: 8px 4px;
    font-size: 0.85rem;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    z-index: 101; /* Higher than sidebar */
    position: relative;
}

.mode-btn:hover {
    background: rgba(255,255,255,0.1);
    color: var(--text-main);
}

.mode-btn.active {
    background: var(--accent);
    color: #1a0f00;
    border-color: var(--accent);
    font-weight: 600;
}

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

button#btn-reset {
    background: transparent;
    border: 1px solid var(--panel-border);
    color: var(--text-muted);
    padding: 10px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    margin-top: 8px;
    width: 100%;
}

button#btn-reset:hover {
    border-color: var(--text-muted);
    color: var(--text-main);
}

.legend h4 {
    font-size: 0.9rem;
    margin: 0 0 12px;
    color: var(--text-main);
}

.legend ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: 10px;
}

.legend-item {
    display: flex;
    align-items: center;
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.color-box {
    width: 12px;
    height: 12px;
    border-radius: 4px;
    margin-right: 10px;
    display: inline-block;
}

.color-box.crust { background: #8b7355; }
.color-box.mantle { background: #ff4500; box-shadow: 0 0 8px #ff4500; }
.color-box.quake { background: #ffffff; border: 2px solid #ff0000; border-radius: 50%; }
.color-box.volcano { background: linear-gradient(to top, #ff4500, #ffcc00); clip-path: polygon(50% 0%, 0% 100%, 100% 100%); }

/* Back Button */
.back-to-home {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 10px 20px;
    background: rgba(20, 30, 50, 0.6);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 999px;
    color: #ffffff;
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    transition: all 0.2s ease;
    z-index: 9999;
    box-shadow: 0 4px 12px rgba(0,0,0,0.2);
    pointer-events: auto;
}

.back-to-home:hover {
    background: rgba(255, 255, 255, 0.15);
    border-color: rgba(255, 255, 255, 0.6);
    transform: translateY(-1px);
    box-shadow: 0 6px 16px rgba(0,0,0,0.3);
}

@media (max-width: 768px) {
    .sidebar {
        top: auto;
        bottom: 0;
        left: 0;
        width: 100%;
        max-height: 60vh;
        border-radius: 20px 20px 0 0;
        transform: translateY(0);
        padding-top: 50px;
    }
    
    .sidebar.collapsed {
        transform: translateY(calc(100% - 70px));
    }

    .sidebar-toggle {
        display: flex;
        top: 15px;
        right: 50%;
        transform: translateX(50%);
    }

    .lang-switcher {
        justify-content: center;
    }

    h1 {
        text-align: center;
        font-size: 1.4rem;
    }

    .eyebrow {
        text-align: center;
    }
}