:root {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-x: #38bdf8;
    --accent-o: #f43f5e;
    --cell-bg: #334155;
    --cell-hover: #475569;
    --border-radius: 16px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden;
}

.container {
    width: 100%;
    max-width: 400px;
    padding: 2rem;
    text-align: center;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    background: linear-gradient(to right, var(--accent-x), var(--accent-o));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.status {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-weight: 600;
}

.player-x { color: var(--accent-x); }
.player-o { color: var(--accent-o); }

.game-board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    background-color: var(--card-bg);
    padding: 12px;
    border-radius: var(--border-radius);
    box-shadow: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
}

.cell {
    aspect-ratio: 1/1;
    background-color: var(--cell-bg);
    border-radius: 8px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 2.5rem;
    font-weight: 800;
    cursor: pointer;
    transition: var(--transition);
}

.cell:hover {
    background-color: var(--cell-hover);
    transform: scale(1.02);
}

.cell.x { color: var(--accent-x); }
.cell.o { color: var(--accent-o); }

.cell.x::before { content: 'X'; }
.cell.o::before { content: 'O'; }

footer {
    margin-top: 2rem;
}

button {
    background-color: var(--card-bg);
    color: var(--text-primary);
    border: 2px solid var(--cell-bg);
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition);
}

button:hover {
    border-color: var(--accent-x);
    background-color: var(--cell-bg);
    transform: translateY(-2px);
}

/* Overlay */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(15, 23, 42, 0.9);
    display: flex;
    justify-content: center;
    align-items: center;
    opacity: 0;
    pointer-events: none;
    transition: var(--transition);
    z-index: 10;
}

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

.overlay-content {
    background-color: var(--card-bg);
    padding: 3rem;
    border-radius: var(--border-radius);
    text-align: center;
    transform: scale(0.8);
    transition: var(--transition);
}

.overlay.active .overlay-content {
    transform: scale(1);
}

.overlay-content h2 {
    font-size: 2rem;
    margin-bottom: 2rem;
}