*,:after,:before{box-sizing:border-box;margin:0;padding:0}:root{--color-bg:#0f0f0f;--color-surface:#1a1a1a;--color-border:#2a2a2a;--color-primary:#6366f1;--color-primary-hover:#818cf8;--color-text:#f0f0f0;--color-muted:#888;--color-again:#ef4444;--color-hard:#f97316;--color-good:#22c55e;--color-easy:#3b82f6}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;background:var(--color-bg);color:var(--color-text);min-height:100vh}a{color:var(--color-primary);text-decoration:none}a:hover{color:var(--color-primary-hover)}button{cursor:pointer;border:none;border-radius:8px;font-size:1rem;font-weight:500;padding:.75rem 1.5rem;transition:opacity .15s}button:hover{opacity:.85}button:disabled{opacity:.4;cursor:not-allowed}input[type=email],input[type=text]{background:var(--color-surface);border:1px solid var(--color-border);border-radius:8px;color:var(--color-text);font-size:1rem;padding:.75rem 1rem;width:100%;outline:none}input:focus{border-color:var(--color-primary)}.card-scene{perspective:1000px;flex:1 1}.card-flip,.card-scene{width:100%;min-height:280px}.card-flip{height:100%;position:relative;transform-style:preserve-3d;transition:transform .45s cubic-bezier(.4,0,.2,1)}.card-flip.is-flipped{transform:rotateY(180deg)}.card-face{position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;background:var(--color-surface);border:1px solid var(--color-border);border-radius:16px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:1.5rem;padding:3rem 2rem}.card-face.card-back{transform:rotateY(180deg)}