:root {
    --ink: #17191c;
    --muted: #737983;
    --line: #e6e8eb;
    --surface: #ffffff;
    --canvas: #f3f5f7;
    --accent: #e9ff5b;
    --danger: #d9363e;
    font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
    color: var(--ink);
    background: var(--canvas);
}

* { box-sizing: border-box; }
body { margin: 0; min-width: 320px; min-height: 100vh; }
button, input { font: inherit; }
button, label { -webkit-tap-highlight-color: transparent; }

.checkout-shell { min-height: 100vh; display: grid; grid-template-columns: minmax(330px, .82fr) minmax(520px, 1.18fr); }
.brand-panel { position: relative; min-height: 100vh; overflow: hidden; padding: clamp(32px, 4.5vw, 72px); background: #17191c; color: #fff; display: flex; flex-direction: column; }
.brand-panel::after { content: ""; position: absolute; width: min(31vw, 470px); aspect-ratio: 1; right: -14%; bottom: 11%; border: 1px solid rgba(255,255,255,.12); border-radius: 50%; box-shadow: 0 0 0 80px rgba(255,255,255,.025), 0 0 0 160px rgba(255,255,255,.018); }
.brand-lockup { display: flex; align-items: center; gap: 12px; font-size: 17px; font-weight: 650; position: relative; z-index: 1; }
.brand-symbol { display: block; width: 40px; height: 40px; border-radius: 6px; object-fit: contain; }
.brand-copy { margin: auto 0; position: relative; z-index: 1; max-width: 520px; }
.eyebrow { margin: 0 0 18px; color: #9da3ac; font-size: 11px; font-weight: 750; letter-spacing: 2px; }
.brand-copy h1 { margin: 0; font-size: clamp(43px, 5vw, 72px); line-height: 1.08; letter-spacing: 0; font-weight: 720; }
.brand-copy > p:last-child { max-width: 410px; margin: 30px 0 0; color: #aeb3ba; line-height: 1.8; font-size: 15px; }
.security-note { position: relative; z-index: 1; color: #8f959e; font-size: 12px; display: flex; gap: 9px; align-items: center; }
.security-note span { color: var(--accent); }

.payment-panel { background: var(--surface); min-height: 100vh; padding: 48px clamp(30px, 7vw, 120px) 28px; display: flex; flex-direction: column; justify-content: center; }
.payment-card { width: 100%; max-width: 560px; margin: auto; }
.payment-card header { margin-bottom: 30px; }
.payment-card .step { color: #858b94; font-size: 12px; font-weight: 650; margin: 0 0 10px; }
.payment-card h2 { font-size: 29px; line-height: 1.25; margin: 0 0 8px; letter-spacing: 0; }
.payment-card header > p:last-child { color: var(--muted); margin: 0; font-size: 14px; }
.alert { padding: 12px 14px; border-left: 3px solid var(--danger); background: #fff4f4; color: #a62930; font-size: 13px; margin-bottom: 22px; }
.field-group { margin: 0 0 24px; padding: 0; border: 0; }
.field-group > label, .field-group legend { display: block; color: #393d42; font-weight: 650; font-size: 13px; margin-bottom: 10px; }
.field-group > label span { color: #a0a4aa; font-weight: 400; margin-left: 5px; }
.amount-input { height: 72px; border: 1px solid #d8dbdf; display: flex; align-items: center; padding: 0 18px; transition: border-color .2s, box-shadow .2s; }
.amount-input:focus-within { border-color: #1e2125; box-shadow: 0 0 0 3px rgba(23,25,28,.07); }
.amount-input.invalid { border-color: var(--danger); }
.amount-input > span { font-size: 25px; font-weight: 550; margin-right: 10px; }
.amount-input input { min-width: 0; flex: 1; border: 0; outline: 0; font-size: 33px; font-weight: 650; color: var(--ink); background: transparent; }
.amount-input input::placeholder { color: #c5c8cc; }
.amount-input em { color: #8b9098; font-size: 12px; font-style: normal; font-weight: 650; }
.field-error { display: block; min-height: 17px; padding-top: 5px; color: var(--danger); font-size: 11px; }
.quick-amounts { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.quick-amounts button { height: 34px; border: 1px solid var(--line); background: #fafafa; color: #5d626a; font-size: 12px; cursor: pointer; transition: .18s ease; }
.quick-amounts button:hover, .quick-amounts button.active { color: #111; border-color: #bbbfc5; background: #f0f1f2; }
.text-input { width: 100%; height: 48px; border: 1px solid #d8dbdf; padding: 0 15px; outline: none; transition: .2s; }
.text-input:focus { border-color: #1e2125; box-shadow: 0 0 0 3px rgba(23,25,28,.07); }
.text-input::placeholder { color: #aeb2b8; }
.field-meta { margin-top: 6px; display: flex; justify-content: space-between; color: #a0a4aa; font-size: 11px; }
.payment-methods { display: grid; grid-template-columns: repeat(3, 1fr); gap: 9px; }
.payment-methods legend { grid-column: 1 / -1; }
.method-option { position: relative; height: 62px; border: 1px solid var(--line); display: flex !important; align-items: center; gap: 8px; padding: 9px 11px; margin: 0 !important; cursor: pointer; transition: .18s ease; }
.method-option:has(input:checked) { border-color: #1d1f22; box-shadow: inset 0 0 0 1px #1d1f22; }
.method-option input { position: absolute; opacity: 0; pointer-events: none; }
.method-icon { flex: 0 0 31px; height: 31px; display: grid; place-items: center; }
.method-icon img { display: block; width: 30px; height: 30px; object-fit: contain; }
.method-name { min-width: 0; font-size: 12px; white-space: nowrap; }
.radio-mark { margin-left: auto; flex: 0 0 14px; height: 14px; border: 1px solid #c6c9cd; border-radius: 50%; box-shadow: inset 0 0 0 3px white; }
.method-option input:checked ~ .radio-mark { background: #202226; border-color: #202226; }
.pay-button { width: 100%; height: 54px; border: 0; border-radius: 4px; padding: 0 18px; background: #1a1c1f; color: white; display: flex; align-items: center; justify-content: center; gap: 9px; font-size: 14px; font-weight: 650; cursor: pointer; text-decoration: none; transition: transform .15s, background .2s; }
.pay-button:hover { background: #2a2d31; }
.pay-button:active { transform: translateY(1px); }
.pay-button:disabled { cursor: wait; opacity: .7; }
.pay-button .arrow { position: absolute; margin-left: min(42vw, 480px); font-size: 19px; font-weight: 400; }
.agreement { color: #a0a4aa; text-align: center; font-size: 11px; margin: 10px 0 0; }
.payment-panel footer { display: flex; justify-content: center; align-items: center; gap: 12px; color: #a1a6ad; font-size: 10px; margin-top: 30px; }
.payment-panel footer i { width: 2px; height: 2px; background: #b8bcc1; border-radius: 50%; }

.result-page { display: grid; place-items: center; background: var(--canvas); padding: 24px; }
.result-card { width: min(100%, 490px); background: white; padding: 54px 46px 42px; text-align: center; box-shadow: 0 18px 60px rgba(30,34,40,.08); }
.result-icon { width: 58px; height: 58px; margin: 0 auto 25px; border-radius: 50%; display: grid; place-items: center; font-size: 24px; font-weight: 700; }
.result-icon.success { background: #e8f9ef; color: #17944c; }.result-icon.failed { background: #fff0f0; color: var(--danger); }
.result-card h1 { font-size: 28px; margin: 0 0 10px; }.result-card .eyebrow { margin-bottom: 12px; }
.result-description { color: var(--muted); font-size: 14px; line-height: 1.7; }
.result-card dl { margin: 30px 0; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.result-card dl div { display: flex; justify-content: space-between; gap: 20px; padding: 13px 0; font-size: 12px; }
.result-card dl div + div { border-top: 1px solid #f0f1f2; }.result-card dt { color: var(--muted); }.result-card dd { margin: 0; word-break: break-all; }
.result-button { position: relative; }.result-button span { position: absolute; right: 18px; font-size: 18px; }

@media (max-width: 820px) {
    .checkout-shell { display: block; }
    .brand-panel { min-height: auto; padding: 22px 20px; }
    .brand-panel::after, .brand-copy, .security-note { display: none; }
    .brand-symbol { width: 36px; height: 36px; }
    .payment-panel { min-height: calc(100vh - 74px); padding: 34px 20px 24px; justify-content: flex-start; }
    .payment-card { margin: 0 auto; }
    .payment-panel footer { margin-top: auto; padding-top: 30px; }
}

@media (max-width: 480px) {
    .payment-panel { padding-left: 16px; padding-right: 16px; }
    .payment-card h2 { font-size: 25px; }
    .amount-input { height: 66px; }.amount-input input { font-size: 30px; }
    .payment-methods { grid-template-columns: 1fr; gap: 7px; }
    .method-option { height: 54px; }
    .result-card { padding: 42px 24px 32px; }
}

@media (prefers-reduced-motion: reduce) { * { scroll-behavior: auto !important; transition: none !important; } }