*{margin:0;padding:0;box-sizing:border-box}
body{background:#0f1117;font-family:'Segoe UI',sans-serif;color:#e8e8e8;height:100vh;overflow:hidden;display:flex;align-items:center;justify-content:center}
.screen{display:none;width:100%;height:100vh;align-items:center;justify-content:center;flex-direction:column}
.screen.active{display:flex}
.box{background:#16181f;border:1px solid #2a3550;border-radius:20px;padding:2.5rem 3rem;text-align:center;max-width:420px;width:90%;box-shadow:0 8px 40px rgba(0,0,0,.5)}
.box h1{font-size:2rem;color:#fff;margin:.5rem 0}
.box p{color:#8a96aa;margin-bottom:1.5rem;line-height:1.6;font-size:.95rem}
button{background:#2a6dd9;color:#fff;border:none;border-radius:10px;padding:.8rem 2.2rem;font-size:1rem;font-weight:700;cursor:pointer;transition:background .2s;display:block;width:100%;margin-bottom:.8rem}
button:hover{background:#3a7de9}
.back-link{color:#4a90e2;font-size:.9rem;text-decoration:none}
#game-screen{flex-direction:column}
#hud{width:100%;max-width:560px;display:flex;justify-content:space-between;align-items:center;padding:.6rem 1rem}
.hud-back{color:#4a90e2;text-decoration:none;font-size:.9rem;font-weight:600}
#score-label,#speed-label{font-size:1rem;font-weight:700;color:#fff}
#toolbar{display:flex;gap:.5rem;margin-bottom:.5rem}
.piece-btn{background:#1e2130;border:2px solid #2a3550;color:#e8e8e8;border-radius:8px;width:48px;height:48px;font-size:1.3rem;cursor:pointer;transition:border-color .15s}
.piece-btn:hover{border-color:#4a90e2}
.piece-btn.active{border-color:#2a6dd9;background:#1a2540;color:#fff}
#canvas{border-radius:12px;border:2px solid #2a3550;display:block;cursor:crosshair}