@import url("https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;700;800&family=Space+Grotesk:wght@500;700&display=swap");

:root {
    --bg: #ffffff;
    --ink: #0b0b0b;
    --muted: #5f6673;
    --subtle: #9aa0aa;
    --line: #e8e8e8;
    --soft: #f5f5f5;
    --accent: #ff3b30;
    --positive: #10b981;
    --font-sans: "Plus Jakarta Sans", "Inter", "Helvetica Neue", Arial, sans-serif;
    --font-mono: "Space Grotesk", "IBM Plex Mono", ui-monospace, monospace;
    --cell: 34px;
}

* {
    box-sizing: border-box;
}

html {
    overflow-x: hidden;
}

body {
    min-height: 100vh;
    margin: 0;
    background: var(--bg);
    color: var(--ink);
    font-family: var(--font-sans);
    overflow-x: hidden;
}

a {
    color: inherit;
    text-decoration: none;
}

.app-topbar {
    min-height: 64px;
    border-bottom: 1px solid var(--line);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 max(16px, calc((100vw - 1180px) / 2));
}

.brand,
.lang-link,
.kicker,
.keyboard-hint,
.board-header,
.board-result,
.ai-lastmove {
    font-family: var(--font-mono);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 1.4px;
    text-transform: uppercase;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--muted);
}

.brand:hover,
.lang-link:hover {
    color: var(--accent);
}

.lang-link {
    color: var(--subtle);
    opacity: 0.6;
}

.arrow-icon {
    width: 14px;
    height: 14px;
    fill: none;
    stroke: currentColor;
    stroke-linecap: round;
    stroke-linejoin: round;
    stroke-width: 2;
}

.app-shell {
    width: min(calc(100% - 64px), 1180px);
    max-width: calc(100vw - 32px);
    margin: 0 auto;
    padding: 64px 0 48px;
}

.hero {
    display: grid;
    grid-template-columns: minmax(0, 8fr) minmax(220px, 3fr);
    gap: 32px;
    align-items: end;
    border-top: 2px solid var(--ink);
    padding-top: 16px;
    margin-bottom: 48px;
}

.hero > *,
.game-toolbar > *,
.rule-panel,
.game-info {
    min-width: 0;
}

.kicker {
    color: var(--accent);
    display: inline-block;
    margin-bottom: 14px;
}

h1 {
    margin: 0;
    font-size: clamp(44px, 7vw, 78px);
    line-height: 0.98;
    letter-spacing: 0;
    font-weight: 800;
    max-width: 100%;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.lead {
    max-width: 680px;
    margin: 22px 0 0;
    color: var(--muted);
    font-size: 17px;
    line-height: 1.58;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.rule-panel {
    border-left: 1px solid var(--line);
    padding-left: 24px;
}

.rule-panel p {
    margin: 0;
    color: var(--muted);
    font-size: 15px;
    line-height: 1.5;
    overflow-wrap: anywhere;
}

.rule-panel strong {
    color: var(--ink);
}

.game-container {
    border-top: 2px solid var(--ink);
    padding-top: 16px;
}

.game-toolbar {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 24px;
    margin-bottom: 24px;
}

button {
    min-height: 42px;
    border: 1px solid var(--ink);
    background: var(--ink);
    color: #fff;
    cursor: pointer;
    font: 800 13px var(--font-sans);
    padding: 0 16px;
    transition: background-color 140ms ease, color 140ms ease, border-color 140ms ease;
}

button:hover:not(:disabled) {
    background: var(--accent);
    border-color: var(--accent);
}

button:disabled {
    cursor: default;
}

.game-info {
    min-height: 42px;
    color: var(--muted);
    text-align: right;
}

#status {
    color: var(--ink);
    font-weight: 800;
}

.keyboard-hint {
    color: var(--subtle);
    margin-top: 4px;
    overflow-wrap: anywhere;
}

.multi-board-container {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 32px;
}

.board-wrapper {
    border-top: 1px solid var(--line);
    padding-top: 14px;
}

.board-header {
    color: var(--ink);
    margin-bottom: 10px;
}

.board {
    width: fit-content;
    border: 1px solid var(--line);
    background: var(--soft);
    padding: 10px;
}

.active-board {
    border-color: var(--accent);
    background: #fff;
}

.inactive-board {
    opacity: 0.52;
}

.completed-board {
    opacity: 0.78;
    border-color: var(--ink);
}

.column-buttons {
    display: grid;
    grid-template-columns: repeat(7, var(--cell));
    gap: 2px;
    margin-bottom: 6px;
}

.column-btn {
    width: var(--cell);
    height: 28px;
    min-height: 28px;
    border: 1px solid var(--line);
    background: #fff;
    color: var(--ink);
    font: 700 11px var(--font-mono);
    padding: 0;
}

.column-btn:hover:not(:disabled),
.column-btn.highlight {
    border-color: var(--accent);
    background: var(--accent);
    color: #fff;
}

.column-btn:disabled {
    background: var(--soft);
    color: var(--subtle);
    border-color: var(--line);
}

.grid {
    display: grid;
    grid-template-columns: repeat(7, var(--cell));
    gap: 2px;
}

.cell {
    width: var(--cell);
    height: var(--cell);
    border: 1px solid var(--line);
    background: #fff;
}

.cell.player-o {
    background: var(--accent);
    border-color: var(--accent);
}

.cell.player-x {
    background: var(--ink);
    border-color: var(--ink);
}

.board-result {
    min-height: 20px;
    margin-top: 10px;
    color: var(--subtle);
}

.board-result.win {
    color: var(--positive);
}

.board-result.lose {
    color: var(--accent);
}

.board-result.tie {
    color: var(--muted);
}

.game-over-message {
    color: var(--accent);
}

.ai-lastmove {
    color: var(--subtle);
    margin-top: 8px;
}

@media (max-width: 760px) {
    :root {
        --cell: min(10.5vw, 34px);
    }

    .app-shell {
        width: min(calc(100% - 48px), 1180px);
        max-width: calc(100vw - 48px);
        padding-top: 48px;
    }

    h1 {
        font-size: clamp(30px, 8.5vw, 38px);
    }

    .lead,
    .rule-panel p,
    .keyboard-hint {
        font-size: 15px;
    }

    .hero,
    .game-toolbar {
        display: block;
    }

    .rule-panel {
        border-left: 0;
        border-top: 1px solid var(--line);
        margin-top: 32px;
        padding: 16px 0 0;
    }

    .game-info {
        margin-top: 16px;
        text-align: left;
    }

    .multi-board-container {
        grid-template-columns: 1fr;
        gap: 28px;
    }
}