:root {
    --board-columns: 15;
    --board-rows: 15;
    --board-width: 600px;
    --board-bg: #f0d9b5;
    --board-border: #8b4513;
    --cell-border: rgba(107, 62, 20, 0.78);
    --cell-hover-bg: rgba(0, 0, 0, 0.1);
    --cell-selected-bg: rgba(0, 255, 0, 0.2);
    --cell-valid-bg: rgba(0, 255, 0, 0.1);
    --cell-last-move-bg: rgba(255, 215, 0, 0.3);
    --piece-size: 78%;
    --gobang-black-piece-top: #66605a;
    --gobang-black-piece-mid: #47423d;
    --gobang-black-piece-bottom: #2f2b28;
    --gobang-white-piece-top: #f7f3eb;
    --gobang-white-piece-mid: #ece5da;
    --gobang-white-piece-bottom: #d8cfc2;
}

.chessboard {
    background:
        radial-gradient(circle at center, rgba(255, 255, 255, 0.12), transparent 70%),
        var(--board-bg);
}

.cell {
    border: none;
    overflow: visible;
    isolation: isolate;
}

.cell::before,
.cell::after {
    content: '';
    position: absolute;
    background-color: var(--cell-border);
    pointer-events: none;
    z-index: 0;
}

.cell::before {
    top: 50%;
    left: 0;
    right: 0;
    height: 1px;
    transform: translateY(-50%);
}

.cell::after {
    top: 0;
    bottom: 0;
    left: 50%;
    width: 1px;
    transform: translateX(-50%);
}

.cell[data-col="0"]::before {
    left: 50%;
}

.cell[data-col="14"]::before {
    right: 50%;
}

.cell[data-row="0"]::after {
    top: 50%;
}

.cell[data-row="14"]::after {
    bottom: 50%;
}

.cell[data-row="3"][data-col="3"],
.cell[data-row="3"][data-col="7"],
.cell[data-row="3"][data-col="11"],
.cell[data-row="7"][data-col="3"],
.cell[data-row="7"][data-col="7"],
.cell[data-row="7"][data-col="11"],
.cell[data-row="11"][data-col="3"],
.cell[data-row="11"][data-col="7"],
.cell[data-row="11"][data-col="11"] {
    background-image: radial-gradient(circle at center, var(--cell-border) 0 9%, transparent 10%);
    background-repeat: no-repeat;
}

.cell:hover,
.cell.selected,
.cell.valid-move,
.cell.last-move {
    background-color: transparent;
}

.turn-indicator.black {
    background-color: #000;
    color: #ffffff;
}

.turn-indicator.white {
    background-color: #fff;
    color: #000000;
}

#turn-order-modal {
    background-color: rgba(26, 26, 26, 0.08);
    pointer-events: none;
}

#turn-order-modal .modal-content {
    width: min(72vw, 220px);
    padding: 1.45rem 1.6rem;
}

#turn-order-modal .modal-content::before {
    inset: 10px;
}

#turn-order-message {
    margin: 0;
    font-size: 1.5rem;
    letter-spacing: 0.18em;
}

.piece {
    width: 100%;
    height: 100%;
    position: relative;
    z-index: 1;
    pointer-events: none;
}

.piece.black {
    background:
        radial-gradient(circle at 34% 28%, rgba(255, 255, 255, 0.24), transparent 34%),
        linear-gradient(150deg, var(--gobang-black-piece-top) 0%, var(--gobang-black-piece-mid) 58%, var(--gobang-black-piece-bottom) 100%);
    color: #f1ece4;
    box-shadow:
        0 7px 16px rgba(47, 43, 40, 0.28),
        inset 0 1px 1px rgba(255, 255, 255, 0.16),
        inset 0 -5px 8px rgba(22, 20, 18, 0.3);
}

.piece.white {
    background:
        radial-gradient(circle at 34% 28%, rgba(255, 255, 255, 0.96), transparent 38%),
        linear-gradient(150deg, var(--gobang-white-piece-top) 0%, var(--gobang-white-piece-mid) 62%, var(--gobang-white-piece-bottom) 100%);
    color: #4f4942;
    border: 1px solid rgba(102, 90, 76, 0.18);
    box-shadow:
        0 7px 16px rgba(116, 104, 92, 0.18),
        inset 0 1px 0 rgba(255, 255, 255, 0.92),
        inset 0 -4px 7px rgba(170, 160, 148, 0.22);
}

.cell.last-move .piece::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 18%;
    height: 18%;
    background-color: rgba(255, 0, 0, 0.7);
    border-radius: 50%;
    z-index: 10;
}

@media (min-width: 1179px) {
    .game-layout {
        container-type: size;
    }

    .chessboard {
        flex: 0 1 auto;
        width: min(100%, 820px, 100cqh);
        max-width: 820px;
        max-height: 100cqh;
        height: auto !important;
        margin: 0 auto;
    }
}

@media (min-width: 1280px) {
    .game-layout {
        gap: clamp(1.6rem, 2vw, 2.4rem);
    }

    .game-sidebar {
        flex: 0 0 220px;
        max-width: 220px;
    }

    .chessboard {
        flex: 0 1 auto;
        width: min(100%, 820px, 100cqh);
        max-width: 820px;
        max-height: 100cqh;
        height: auto !important;
        margin: 0 auto;
    }
}

@media (min-width: 1179px) and (max-height: 850px) {
    .game-layout {
        align-items: flex-start;
    }
}