:root{--bg:#f4f6fb;--card:#fff;--ink:#0f172a;--muted:#64748b;--brand:#2f5bea;--brand-ink:#fff;--border:#e2e8f0;--danger:#dc2626;--ok:#059669}*{box-sizing:border-box}body,html{margin:0;padding:0;background:var(--bg);color:var(--ink);font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif}.page{min-height:100vh;display:flex;align-items:center;justify-content:center;padding:24px}.card{width:100%;max-width:420px;background:var(--card);border:1px solid var(--border);border-radius:16px;box-shadow:0 10px 40px rgba(15,23,42,.08);padding:28px}.brand{font-size:18px;letter-spacing:-.01em}.amount,.brand{font-weight:700}.amount{font-size:32px;letter-spacing:-.02em;margin:4px 0 0}.muted{color:var(--muted);font-size:14px}.pay-btn{width:100%;margin-top:20px;padding:12px 16px;border:0;border-radius:10px;background:var(--brand);color:var(--brand-ink);font-size:15px;font-weight:600;cursor:pointer}.pay-btn:disabled{opacity:.6;cursor:not-allowed}.error{color:var(--danger);font-size:14px;margin-top:12px}.success{color:var(--ok);font-weight:600}