:root{--primary: #1877f2;--primary-dark: #145dbf;--bg: #f0f2f5;--card: #ffffff;--text: #1c1e21;--muted: #65676b;--border: #dddfe2;--success: #31a24c;--danger: #e41e3f;--radius: 12px}*{margin:0;padding:0;box-sizing:border-box}body{font-family:Segoe UI,Padauk,system-ui,sans-serif;background:var(--bg);color:var(--text);-webkit-font-smoothing:antialiased}.app{max-width:480px;margin:0 auto;min-height:100vh;background:var(--bg);padding-bottom:80px}.topbar{position:sticky;top:0;z-index:10;background:var(--primary);color:#fff;padding:14px 16px;font-size:1.1rem;font-weight:700;display:flex;align-items:center;justify-content:space-between;box-shadow:0 2px 6px #0000001a}.topbar a{color:#fff;text-decoration:none;font-size:.9rem}.content{padding:16px}.book-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px}.book-card{background:var(--card);border-radius:var(--radius);overflow:hidden;box-shadow:0 1px 4px #00000014;display:flex;flex-direction:column}.book-cover{aspect-ratio:3 / 4;background:linear-gradient(135deg,#e0e7ff,#c7d2fe);display:flex;align-items:center;justify-content:center;font-size:2.5rem;object-fit:cover;width:100%}.book-info{padding:10px;flex:1;display:flex;flex-direction:column;gap:4px}.book-title{font-size:.92rem;font-weight:600;line-height:1.3}.book-author{font-size:.78rem;color:var(--muted)}.book-price{font-weight:700;color:var(--primary);margin-top:auto}.stock-out{color:var(--danger);font-size:.75rem}.btn{border:none;border-radius:8px;padding:12px 16px;font-size:.95rem;font-weight:600;cursor:pointer;background:var(--primary);color:#fff;width:100%;transition:background .15s}.btn:hover{background:var(--primary-dark)}.btn:disabled{background:#b0b3b8;cursor:not-allowed}.btn-outline{background:#fff;color:var(--primary);border:1px solid var(--primary)}.btn-success{background:var(--success)}.btn-sm{padding:8px 10px;font-size:.85rem;width:auto}.cart-bar{position:fixed;bottom:0;left:50%;transform:translate(-50%);width:100%;max-width:480px;background:#fff;border-top:1px solid var(--border);padding:12px 16px;display:flex;align-items:center;gap:12px;box-shadow:0 -2px 8px #0000000f}.cart-bar .total{flex:1;font-weight:700}.field{margin-bottom:14px}.field label{display:block;font-size:.85rem;font-weight:600;margin-bottom:6px;color:var(--muted)}.field input,.field textarea,.field select{width:100%;padding:12px;border:1px solid var(--border);border-radius:8px;font-size:1rem;font-family:inherit}.field input:focus,.field textarea:focus{outline:2px solid var(--primary);border-color:transparent}.field .err{color:var(--danger);font-size:.8rem;margin-top:4px}.card{background:#fff;border-radius:var(--radius);padding:16px;margin-bottom:16px;box-shadow:0 1px 4px #0000000f}.row{display:flex;justify-content:space-between;align-items:center;padding:8px 0}.row+.row{border-top:1px solid var(--border)}.qty{display:flex;align-items:center;gap:8px}.qty button{width:30px;height:30px;border-radius:6px;border:1px solid var(--border);background:#fff;font-size:1.1rem;cursor:pointer}.muted{color:var(--muted);font-size:.85rem}.center{text-align:center}.qr-img{width:240px;height:240px;display:block;margin:12px auto;border-radius:8px}.alert{padding:12px;border-radius:8px;margin-bottom:12px;font-size:.9rem}.alert-success{background:#e3f5e9;color:#1a7a37}.alert-error{background:#fde7ea;color:var(--danger)}.alert-info{background:#e7f0fd;color:var(--primary-dark)}.badge{display:inline-block;padding:3px 10px;border-radius:999px;font-size:.75rem;font-weight:600}.badge-pending{background:#fff3cd;color:#856404}.badge-paid{background:#d4edda;color:#155724}.badge-cancelled{background:#f8d7da;color:#721c24}.spinner{text-align:center;padding:40px;color:var(--muted)}.pay-option{display:flex;gap:12px;align-items:center;border:2px solid var(--border);border-radius:10px;padding:14px;margin-bottom:12px;cursor:pointer}.pay-option.selected{border-color:var(--primary);background:#f0f6ff}.pay-option .icon{font-size:1.6rem}