:root{--bg:#02080d;--panel:#061118;--green:#00ef9d;--cyan:#00c9ff;--yellow:#ffd400;--pink:#ff3aa7;--text:#f4f7f8;--muted:#a8b8be;font-family:"Segoe UI",system-ui,sans-serif}*{box-sizing:border-box}body{margin:0;color:var(--text);background:radial-gradient(circle at 20% 10%,rgba(0,239,157,.1),transparent 30%),var(--bg)}.shell{width:min(1100px,calc(100% - 28px));margin:auto;padding:24px 0 50px}nav{display:flex;justify-content:space-between;gap:14px;padding:12px 0;color:var(--muted);font-size:.82rem}nav a{color:var(--cyan)}header,.exercise,.help{border:1px solid rgba(0,239,157,.25);border-radius:22px;background:rgba(6,17,24,.95);padding:clamp(22px,4vw,42px);margin-bottom:18px}.eyebrow{color:var(--cyan);text-transform:uppercase;letter-spacing:.13em}h1{font-size:clamp(2.8rem,8vw,6rem);line-height:.9;margin:.2em 0;color:var(--green)}header p{max-width:750px;color:var(--muted);line-height:1.6}.transport{display:flex;gap:10px;margin-top:20px}button{font:inherit}.transport button,.tab{border:1px solid var(--green);background:transparent;color:var(--green);border-radius:10px;padding:11px 18px;font-weight:700;cursor:pointer}.transport button:disabled{opacity:.4}.tabs{display:flex;gap:10px;margin:24px 0}.tab.active{background:var(--green);color:#00110b}.exercise{display:none}.exercise.active{display:block}.bit-grid{display:grid;grid-template-columns:1fr 1fr;gap:30px;max-width:700px;margin:auto}.coin{aspect-ratio:1;border-radius:50%;border:4px solid var(--green);display:flex;flex-direction:column;align-items:center;justify-content:center;cursor:pointer;transition:.12s}.coin strong{font-size:clamp(4rem,12vw,8rem)}.coin span{text-transform:uppercase;letter-spacing:.12em}.coin small{margin-top:8px}.coin.zero{background:#000;color:#fff}.coin.one{background:#fff;color:#000;border-color:#fff}.coin.active,.key.active{transform:translateY(4px);box-shadow:0 0 30px rgba(0,239,157,.55)}.message{text-align:center;color:var(--muted)}.piano{display:grid;grid-template-columns:repeat(8,1fr);gap:6px;min-height:280px}.key{border:2px solid #111;background:#fff;color:#050505;border-radius:0 0 10px 10px;display:flex;flex-direction:column;justify-content:flex-end;align-items:center;padding:18px 4px;cursor:pointer}.key strong{font-size:1.1rem}.key span{font-size:.75rem;margin-top:8px}.song-card,.help{color:var(--muted)}.song-card{margin-top:24px;padding:20px;border:1px solid rgba(0,201,255,.25);border-radius:14px}.song-card h2,.help h2{color:var(--text)}code{color:var(--yellow);font-size:1rem}@media(max-width:700px){nav{flex-direction:column}.bit-grid{gap:14px}.piano{overflow-x:auto;grid-template-columns:repeat(8,70px)}.coin strong{font-size:3.8rem}}