:root {
    --bg-start: #1a1c29;
    --bg-end: #0d0e14;
    --card-bg: #21232f;
    --cell-dead: #2b2e3d;
    --cell-border: #363a4a;
    --cell-live: #2ee6a6;
    --cell-live-glow: rgba(46, 230, 166, 0.55);
    --text-primary: #f2f3f7;
    --text-muted: #8b8fa3;
    --accent: #5b7cfa;
    --accent-hover: #7590ff;
    --ant-color: #ff6b6b;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 32px 16px;
    background: radial-gradient(circle at top, var(--bg-start), var(--bg-end));
    font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
    color: var(--text-primary);
}

.app {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;
    width: 100%;
    max-width: 760px;
}

.app-header {
    text-align: center;
}

.back-link {
    display: inline-block;
    margin-bottom: 8px;
    color: var(--text-muted);
    font-size: 0.85rem;
    text-decoration: none;
}

.back-link:hover {
    color: var(--accent-hover);
}

.app-header h1 {
    margin: 0;
    font-size: 2rem;
    font-weight: 600;
    letter-spacing: 0.02em;
}

.subtitle {
    margin: 4px 0 0;
    color: var(--text-muted);
    font-size: 0.95rem;
}

.board-card {
    padding: 16px;
    background: var(--card-bg);
    border-radius: 16px;
    box-shadow: 0 20px 45px rgba(0, 0, 0, 0.45);
    width: fit-content;
    max-width: 100%;
    overflow: auto;
}

.board {
    display: grid;
    gap: 2px;
}

.cell {
    width: 10px;
    height: 10px;
    background-color: var(--cell-dead);
    border: 1px solid var(--cell-border);
    border-radius: 2px;
    cursor: pointer;
    transition: background-color 0.15s ease, box-shadow 0.15s ease, transform 0.1s ease;
}

.cell:hover {
    transform: scale(1.15);
}

.cell.live {
    background-color: var(--cell-live);
    border-color: var(--cell-live);
    border-radius: 4px;
    box-shadow: 0 0 8px var(--cell-live-glow);
}

.controls {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
}

.btn {
    padding: 10px 24px;
    border: none;
    border-radius: 999px;
    font-size: 0.95rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: transform 0.12s ease, box-shadow 0.12s ease, background-color 0.15s ease;
}

.btn:active {
    transform: translateY(1px);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent), var(--accent-hover));
    color: #fff;
    box-shadow: 0 8px 20px rgba(91, 124, 250, 0.4);
}

.btn-primary:hover {
    box-shadow: 0 10px 24px rgba(91, 124, 250, 0.55);
}

.btn-secondary {
    background: var(--card-bg);
    color: var(--text-primary);
    border: 1px solid var(--cell-border);
}

.btn-secondary:hover {
    background: var(--cell-dead);
}