:root {
    --gap-inner: 3px;
    --gap-outer: 8px;
    --radius: 8px;
    --color-x: #4caf50;
    --color-o: #e53935;
    --color-bg: #f5f5f5;
    --color-surface: #fff;
    --color-border: #ccc;
    --color-active-border: #2196f3;
    --color-active-bg: #e3f2fd;
    --color-won-x: rgba(76, 175, 80, 0.15);
    --color-won-o: rgba(229, 57, 53, 0.15);
}

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

body {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100dvh;
    background-color: var(--color-bg);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    color: #333;
    padding: 12px;
}

/* Header / status bar */
.status-bar {
    text-align: center;
    margin-bottom: 12px;
}

.status-bar h1 {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 2px;
}

.turn-indicator {
    font-size: 0.95rem;
    color: #666;
}

.turn-indicator .player-x { color: var(--color-x); font-weight: 600; }
.turn-indicator .player-o { color: var(--color-o); font-weight: 600; }

/* Meta board (3x3 grid of sub-boards) */
.game-board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--gap-outer);
    padding: 10px;
    background-color: var(--color-surface);
    border-radius: 12px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
    width: min(96vw, 500px);
}

/* Individual sub-board */
.sub-board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--gap-inner);
    padding: 5px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius);
    transition: border-color 0.2s, background-color 0.2s, opacity 0.2s;
    position: relative;
}

/* When a specific board is targeted, dim all non-active, non-won boards */
.game-board.has-target .sub-board:not(.active):not(.won-x):not(.won-o) {
    opacity: 0.4;
}

.sub-board.active {
    border-color: var(--color-active-border);
    background-color: var(--color-active-bg);
    box-shadow: 0 0 0 2px rgba(33, 150, 243, 0.25);
}

.sub-board.won-x {
    background-color: var(--color-won-x);
    border-color: var(--color-x);
}

.sub-board.won-o {
    background-color: var(--color-won-o);
    border-color: var(--color-o);
}

.sub-board.won-x .cell,
.sub-board.won-o .cell {
    cursor: default;
    opacity: 0.4;
}

/* Individual cell — use aspect-ratio so they scale fluidly */
.cell {
    aspect-ratio: 1;
    width: 100%;
    border: 1px solid #e0e0e0;
    border-radius: 4px;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    user-select: none;
    font-size: clamp(0.85rem, 2.5vw, 1.3rem);
    font-weight: 700;
    transition: background-color 0.15s;
    background-color: var(--color-surface);
}

.cell:hover {
    background-color: #f0f0f0;
}

.cell.x {
    color: var(--color-x);
    background-color: rgba(76, 175, 80, 0.08);
}

.cell.o {
    color: var(--color-o);
    background-color: rgba(229, 57, 53, 0.08);
}

/* Won sub-board overlay label */
.sub-board-winner {
    position: absolute;
    inset: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: clamp(1.8rem, 8vw, 3rem);
    font-weight: 800;
    z-index: 1;
    pointer-events: none;
}

.sub-board-winner.x { color: var(--color-x); }
.sub-board-winner.o { color: var(--color-o); }

/* Footer */
footer {
    margin-top: 12px;
    text-align: center;
}

footer a {
    color: #666;
    text-decoration: none;
    font-size: 0.9rem;
}

footer a:hover {
    color: #333;
    text-decoration: underline;
}

/* Modal */
.modal-overlay {
    display: none;
    position: fixed;
    z-index: 100;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.4);
}

.modal-overlay.visible {
    display: flex;
    justify-content: center;
    align-items: center;
}

.modal {
    background: var(--color-surface);
    border-radius: 12px;
    padding: 24px 28px;
    max-width: 400px;
    width: 90%;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.15);
}

.modal h2 {
    font-size: 1.15rem;
    margin-bottom: 10px;
}

.modal p, .modal li {
    font-size: 0.9rem;
    line-height: 1.5;
    color: #555;
}

.modal ul {
    padding-left: 20px;
    margin-top: 8px;
}

.modal-close {
    float: right;
    background: none;
    border: none;
    font-size: 1.4rem;
    cursor: pointer;
    color: #999;
    line-height: 1;
}

.modal-close:hover {
    color: #333;
}

/* Game-over banner */
.game-over-banner {
    margin-top: 12px;
    padding: 12px 24px;
    border-radius: var(--radius);
    font-size: 1.1rem;
    font-weight: 600;
    text-align: center;
    animation: fadeIn 0.3s ease;
}

.game-over-banner.win {
    background-color: rgba(76, 175, 80, 0.15);
    color: var(--color-x);
}

.game-over-banner.lose {
    background-color: rgba(229, 57, 53, 0.15);
    color: var(--color-o);
}

.game-over-banner.draw {
    background-color: rgba(0, 0, 0, 0.08);
    color: #666;
}

.game-over-banner button {
    margin-top: 8px;
    padding: 6px 20px;
    border: none;
    border-radius: 4px;
    background: #333;
    color: #fff;
    font-size: 0.85rem;
    cursor: pointer;
}

.game-over-banner button:hover {
    background: #555;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-8px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* Small screens */
@media (max-width: 520px) {
    body {
        padding: 8px;
    }

    .status-bar h1 { font-size: 1.1rem; }

    .game-board {
        width: 100vw;
        border-radius: 0;
        padding: 6px;
        gap: 5px;
    }

    .sub-board {
        padding: 3px;
        gap: 2px;
    }
}