*{box-sizing:border-box}body{margin:0;min-height:100vh;display:flex;align-items:center;justify-content:center;font-family:system-ui,-apple-system,Segoe UI,sans-serif;background:#f4f5f7;color:#1a1a1a}.game{display:flex;flex-direction:column;align-items:center;gap:16px;padding:32px}h1{margin:0;font-size:28px}.status{font-size:18px;font-weight:600;min-height:24px}.mode-select,.difficulty-select{display:flex;gap:8px;background:#e4e6ea;padding:4px;border-radius:8px}.mode-btn,.difficulty-btn{padding:6px 16px;font-size:14px;font-weight:600;border:none;border-radius:6px;background:transparent;color:#555;cursor:pointer;transition:background-color .15s ease,color .15s ease}.mode-btn:hover,.difficulty-btn:hover{color:#1a1a1a}.mode-btn--active,.difficulty-btn--active{background:#fff;color:#1a1a1a;box-shadow:0 1px 3px #00000026}.board{display:grid;grid-template-columns:repeat(3,96px);grid-template-rows:repeat(3,96px);gap:6px;background:#d0d3d8;padding:6px;border-radius:8px}.square{background:#fff;border:none;border-radius:4px;font-size:36px;font-weight:700;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:background-color .15s ease}.square:hover{background:#f0f0f0}.square--win{background:#bdf0c6;color:#1a7d34}.restart{padding:8px 20px;font-size:15px;border-radius:6px;border:1px solid #ccc;background:#fff;cursor:pointer}.restart:hover{background:#f0f0f0}