:root {
    --bg: #0d0d1a;
    --grid: #1f1f3a;
    --text: #e0e0e0;
    --accent: #00d4ff;
    --accent-dim: #00a8cc;
    --ghost: rgba(0, 212, 255, 0.25);
    --ghost-border: rgba(0, 212, 255, 0.5);
    --piece-I: #00f0f0;
    --piece-J: #0000f0;
    --piece-L: #f0a000;
    --piece-O: #f0f000;
    --piece-S: #00f000;
    --piece-T: #a000f0;
    --piece-Z: #f00000;
    --overlay-bg: rgba(13, 13, 26, 0.95);
    --btn-bg: #1a1a3a;
    --btn-hover: #2a2a5a;
    --btn-text: #e0e0e0;
    --font-mono: 'IBM Plex Mono', 'Fira Code', monospace;
    --font-ui: 'Outfit', system-ui, sans-serif;
}

@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;600;700&family=Outfit:wght@400;600;700&display=swap');

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

html, body {
    height: 100%;
    background: var(--bg);
    color: var(--text);
    font-family: var(--font-ui);
    touch-action: none;
    overscroll-behavior: none;
    -webkit-tap-highlight-color: transparent;
}

#game {
    display: block;
    max-width: 95vw;
    max-height: 90vh;
    margin: auto;
    image-rendering: pixelated;
    image-rendering: crisp-edges;
}

#touch-zones {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 5;
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-template-rows: 1fr 1fr;
}

#touch-zones .zone {
    pointer-events: none;
    touch-action: none;
}

#touch-zones .left  { grid-column: 1; grid-row: 2; }
#touch-zones .right { grid-column: 2; grid-row: 2; }
#touch-zones .rotate { grid-column: 1 / 3; grid-row: 1; }
#touch-zones .drop  { grid-column: 1 / 3; grid-row: 2; opacity: 0; }

@media (hover: none) and (pointer: coarse) {
    #touch-zones .drop { opacity: 0.01; }
}

.overlay {
    position: fixed;
    inset: 0;
    background: var(--overlay-bg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1.5rem;
    z-index: 10;
    text-align: center;
    padding: 2rem;
}

.overlay.hidden {
    display: none;
}

.overlay h2 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent);
    text-shadow: 0 0 20px var(--accent);
    font-family: var(--font-ui);
}

.overlay p {
    font-size: 1.2rem;
    color: var(--text);
    opacity: 0.9;
    font-family: var(--font-ui);
}

.overlay kbd {
    background: var(--btn-bg);
    border: 1px solid var(--accent-dim);
    border-radius: 4px;
    padding: 0.2rem 0.5rem;
    font-family: var(--font-mono);
    font-size: 0.9em;
    color: var(--accent);
}

button {
    background: var(--btn-bg);
    border: 2px solid var(--accent-dim);
    border-radius: 8px;
    color: var(--btn-text);
    font-family: var(--font-ui);
    font-size: 1.2rem;
    font-weight: 600;
    padding: 0.75rem 2.5rem;
    cursor: pointer;
    transition: background 0.15s, border-color 0.15s, transform 0.05s;
    min-width: 200px;
}

button:hover, button:focus {
    background: var(--btn-hover);
    border-color: var(--accent);
    outline: none;
}

button:active {
    transform: scale(0.98);
}

#rotate-prompt {
    z-index: 20;
}

@media (orientation: landscape) and (max-height: 500px) {
    #rotate-prompt:not(.hidden) {
        display: flex;
    }

    #game, #touch-zones, #pause-overlay, #gameover-overlay, .nav-btn {
        display: none !important;
    }
}

@media (max-width: 480px) {
    .overlay h2 { font-size: 2rem; }
    .overlay p { font-size: 1rem; }
    button { font-size: 1rem; min-width: 180px; padding: 0.6rem 1.5rem; }
}

/* ===== 네비게이션 버튼 ===== */
.nav-btn {
    position: fixed;
    top: 24px;
    left: 24px;
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 7px 20px;
    font-size: 13px;
    font-weight: bold;
    letter-spacing: 1px;
    border: 1px solid rgba(0, 212, 255, 0.3);
    border-radius: 20px;
    cursor: pointer;
    background: rgba(0, 212, 255, 0.08);
    color: #00d4ff;
    text-decoration: none;
    z-index: 10;
    transition: background 0.3s, border-color 0.3s, transform 0.15s;
}

.nav-btn:hover {
    background: rgba(0, 212, 255, 0.18);
    border-color: rgba(0, 212, 255, 0.5);
}

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

.nav-icon {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
}

.home-link {
    left: 24px;
}

.clock-link {
    left: 120px;
}

@media (max-width: 480px) {
    .nav-btn { font-size: 11px; padding: 5px 16px; gap: 5px; }
    .nav-icon { width: 14px; height: 14px; }
    .home-link { left: 16px; top: 16px; }
    .clock-link { left: 100px; top: 16px; }
}