:root {
    --bg: #111;
    --panel: #161616;
    --ink: #eaeaea;
    --muted: #9aa3a7;
    --accent: #ff8a1f;
    --danger: #ff5a5a;

    --grid: #2a2a2a;
    --grid-strong: #3a3a3a;
    --sq-light: #3d3d3d;
    --sq-dark: #252525;
    --radius: 14px;
    --shadow: 0 12px 30px rgba(0, 0, 0, .35);
}

* {
    box-sizing: border-box;
}

html, body {
    height: 100%;
}

html, body, button, select {
    font-family: Inter, system-ui, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--ink);
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.app {
    max-width: 720px;
    margin: 0 auto;
    padding: 20px 16px 40px;
}

.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
}

.topbar h1 {
    margin: 0;
    font-size: 24px;
    letter-spacing: .5px;
}

.topbar .brand {
    display: flex;
    align-items: center;
    gap: 10px;
}

.brand-icon {
    font-size: 28px;
    line-height: 1;
    color: var(--accent);
}

.lang-switch select {
    background: var(--panel);
    color: var(--ink);
    border: 1px solid var(--grid-strong);
    border-radius: 10px;
    padding: 8px 10px;
}

.controls {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 14px;
    flex-wrap: wrap;
}

.difficulty {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.chip {
    background: #151515;
    color: var(--ink);
    border: 1px solid var(--grid);
    padding: 8px 10px;
    border-radius: 999px;
    cursor: pointer;
    font-size: 14px;
}

.chip:hover {
    border-color: var(--grid-strong);
}

.chip.active {
    border-color: var(--accent);
    box-shadow: 0 0 0 1px var(--accent) inset;
}

.actions {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.btn {
    background: linear-gradient(180deg, #1a1a1a, #141414);
    border: 1px solid var(--grid-strong);
    color: var(--ink);
    padding: 10px 16px;
    border-radius: 12px;
    cursor: pointer;
    font-size: 15px;
}

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

.btn:active {
    transform: translateY(1px);
}

.btn-ghost {
    background: transparent;
    color: var(--muted);
}

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

.board-wrap {
    display: flex;
    justify-content: center;
}

.board-panel {
    width: 100%;
    max-width: 560px;
}

#board {
    width: 100%;
    max-width: 560px;
    margin: 0 auto;
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
}

/* chessboard.js 1.0 — dark squares */
#board .white-1e1d7 {
    background-color: var(--sq-light) !important;
}

#board .black-3c85d {
    background-color: var(--sq-dark) !important;
}

/* chessboard.js — no slide/fade when position updates */
#board img,
#board [class*="piece-"] {
    transition: none !important;
    animation: none !important;
}

.status {
    margin: 14px 0 0;
    text-align: center;
    font-size: 16px;
    color: var(--muted);
    min-height: 1.4em;
}

.status.is-accent {
    color: var(--accent);
}

.status.is-danger {
    color: var(--danger);
}

.end-overlay,
.promo-overlay {
    position: fixed;
    inset: 0;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(0, 0, 0, .72);
    padding: 16px;
}

.end-overlay[hidden],
.promo-overlay[hidden] {
    display: none;
}

.end-card,
.promo-card {
    background: var(--panel);
    border: 1px solid var(--grid-strong);
    border-radius: var(--radius);
    padding: 24px 28px;
    text-align: center;
    box-shadow: var(--shadow);
    max-width: 360px;
    width: 100%;
}

.end-title {
    margin: 0 0 18px;
    font-size: 22px;
}

.promo-card h2 {
    margin: 0 0 16px;
    font-size: 18px;
    font-weight: 600;
}

.promo-pieces {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.promo-btn {
    width: 64px;
    height: 64px;
    border: 2px solid var(--grid-strong);
    border-radius: 12px;
    background: var(--bg);
    cursor: pointer;
    padding: 4px;
    transition: border-color .15s;
}

.promo-btn:hover {
    border-color: var(--accent);
}

.promo-btn img {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

@media (max-width: 480px) {
    .topbar h1 {
        font-size: 20px;
    }

    .chip {
        padding: 6px 8px;
        font-size: 13px;
    }
}