:root {
    --cell-size: 100px;
    --board-gap: 12px;
}

@media (min-width: 768px) {
    :root {
        --cell-size: 140px;
        --board-gap: 16px;
    }
}

.game-board {
    display: grid;
    grid-template-columns: repeat(3, var(--cell-size));
    grid-template-rows: repeat(3, var(--cell-size));
    gap: var(--board-gap);
    position: relative;
}

.cell {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2.5rem;
    font-weight: 800;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    position: relative;
    overflow: hidden;
}

.cell:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

.cell:active {
    transform: scale(0.95);
}

.cell.x::after {
    content: "X";
    color: var(--brand-accent);
}

.cell.o::after {
    content: "O";
    color: rgba(255, 255, 255, 0.4);
}

.cell.x, .cell.o {
    cursor: default;
    pointer-events: none;
}

/* Animations */
@keyframes markAppear {
    0% { transform: scale(0.5); opacity: 0; }
    100% { transform: scale(1); opacity: 1; }
}

.cell.x::after, .cell.o::after {
    animation: markAppear 0.4s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

#winner-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

#winner-overlay.active h2 {
    animation: tiltIn 0.8s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

@keyframes tiltIn {
    0% { transform: translateY(40px) skewY(2deg); opacity: 0; }
    100% { transform: translateY(0) skewY(0); opacity: 1; }
}