:root {
  color-scheme: light;
  --background: #f3f7f6;
  --surface: #ffffff;
  --ink: #162d34;
  --muted: #52676d;
  --teal: #126a68;
  --teal-soft: #e2f2ee;
  --line: #d5e4e2;
  --accent: #be713c;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--background); color: var(--ink); font: 16px/1.55 "Segoe UI", "Microsoft YaHei", sans-serif; }
button, input { font: inherit; }
a { color: inherit; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }

.page-shell { max-width: 1184px; margin: 0 auto; padding: 0 28px; }
.site-header { min-height: 82px; display: flex; align-items: center; justify-content: space-between; gap: 24px; border-bottom: 1px solid var(--line); }
.brand { display: inline-flex; align-items: center; gap: 12px; font-weight: 740; font-size: 19px; text-decoration: none; white-space: nowrap; }
.brand-mark { width: 35px; height: 35px; display: grid; place-items: center; border: 2px solid var(--teal); border-radius: 9px; color: var(--teal); font: 700 18px/1 Consolas, monospace; }
.brand-mark span { color: var(--accent); }
.header-link { color: var(--teal); font-size: 14px; font-weight: 650; text-underline-offset: 4px; white-space: nowrap; }
.header-link:hover, .source-links a:hover { color: #084e4c; }

.intro { padding: 65px 0 46px; max-width: 760px; }
.eyebrow, .section-index { margin: 0; color: var(--teal); font: 700 12px/1.4 Consolas, "Courier New", monospace; letter-spacing: .1em; text-transform: uppercase; }
h1, h2, h3, p { overflow-wrap: break-word; }
h1 { margin: 16px 0; font-size: clamp(34px, 5vw, 60px); line-height: 1.13; letter-spacing: -.04em; }
.intro-copy { max-width: 630px; margin: 0; color: var(--muted); font-size: 17px; line-height: 1.7; }

.workspace { display: grid; grid-template-columns: minmax(300px, 360px) minmax(0, 1fr); gap: 20px; align-items: start; }
.panel { min-width: 0; background: var(--surface); border: 1px solid var(--line); border-radius: 18px; box-shadow: 0 10px 28px rgba(22, 45, 52, .035); }
.usage-panel { padding: 29px; }
.results-panel { overflow: hidden; }
.panel-heading h2, .method h2, .sources h2 { margin: 8px 0 0; font-size: 23px; line-height: 1.25; letter-spacing: -.025em; }
.usage-panel form { margin-top: 32px; }
.field + .field { margin-top: 21px; }
.field label { display: block; margin-bottom: 8px; font-weight: 650; }
.field input { display: block; width: 100%; min-height: 48px; padding: 10px 14px; border: 1px solid #b9d0cc; border-radius: 10px; background: #fff; color: var(--ink); font: 600 18px/1.3 Consolas, "Microsoft YaHei", monospace; }
.field input:focus { border-color: var(--teal); }
.field-note { margin: 6px 0 0; color: var(--muted); font-size: 13px; }
.calculate-button { width: 100%; min-height: 49px; margin-top: 30px; border: 0; border-radius: 10px; background: var(--teal); color: #fff; font-weight: 700; cursor: pointer; transition: background .18s ease, transform .18s ease; }
.calculate-button:hover { background: #0b5553; }
.calculate-button:active { transform: translateY(1px); }
.form-error { margin: 12px 0 0; color: #a43f2c; font-size: 14px; }

.results-heading { display: flex; align-items: end; justify-content: space-between; flex-wrap: wrap; gap: 12px; padding: 29px 30px 23px; }
.currency-tag { color: var(--muted); font: 600 12px/1.4 Consolas, "Microsoft YaHei", monospace; }
.result-row { display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 18px 30px; border-top: 1px solid var(--line); }
.result-row:nth-child(even) { background: #fafdfe; }
.model-info { min-width: 0; }
.provider { color: var(--teal); font: 700 11px/1.3 Consolas, monospace; letter-spacing: .07em; text-transform: uppercase; }
.model-info h3 { margin: 3px 0 2px; font-size: 17px; line-height: 1.3; }
.rate { margin: 0; color: var(--muted); font-size: 12px; }
.monthly-cost { margin: 0; flex: 0 0 auto; color: var(--ink); font: 700 clamp(20px, 2.4vw, 28px)/1.2 Consolas, "Microsoft YaHei", monospace; font-variant-numeric: tabular-nums; }

.method { margin-top: 25px; padding: 28px 30px; border-left: 4px solid var(--accent); background: var(--teal-soft); border-radius: 0 14px 14px 0; }
.formula { margin: 20px 0 8px; font: 600 15px/1.7 Consolas, "Microsoft YaHei", monospace; }
.method-note { margin: 0; color: var(--muted); font-size: 13px; }
.sources { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 18px 38px; padding: 48px 0 52px; }
.sources > p { margin: 24px 0 0; color: var(--muted); font-size: 14px; }
.source-links { display: flex; align-items: end; flex-wrap: wrap; gap: 10px 26px; width: 100%; }
.source-links a { color: var(--teal); font-size: 14px; font-weight: 650; text-underline-offset: 4px; }
.site-footer { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px 24px; padding: 22px 0 38px; border-top: 1px solid var(--line); color: var(--muted); font-size: 13px; }
.site-footer a { color: var(--teal); font-weight: 650; text-underline-offset: 3px; }

.article-layout { max-width: 840px; margin: 0 auto; padding: 55px 0 70px; }
.article-card { padding: clamp(24px, 5vw, 58px); background: var(--surface); border: 1px solid var(--line); border-radius: 18px; box-shadow: 0 10px 28px rgba(22, 45, 52, .035); }
.article-card h1 { margin: 15px 0 18px; font-size: clamp(32px, 5vw, 49px); }
.article-lead { margin: 0; color: var(--muted); font-size: 18px; line-height: 1.8; }
.article-body { margin-top: 38px; font-size: 16px; line-height: 1.9; }
.article-body h2 { margin: 36px 0 10px; font-size: 23px; line-height: 1.35; }
.article-body p { margin: 0 0 18px; }
.article-body code { padding: 1px 5px; border-radius: 4px; background: var(--teal-soft); font: .9em/1.6 Consolas, monospace; overflow-wrap: anywhere; }
.article-links { display: flex; flex-wrap: wrap; gap: 12px 24px; margin-top: 38px; padding-top: 22px; border-top: 1px solid var(--line); }
.article-links a { color: var(--teal); font-weight: 650; text-underline-offset: 4px; overflow-wrap: anywhere; }

@media (max-width: 760px) {
  .page-shell { padding: 0 16px; }
  .site-header { min-height: 66px; }
  .intro { padding: 43px 2px 30px; }
  .intro-copy { font-size: 16px; }
  .workspace { grid-template-columns: 1fr; gap: 15px; }
  .usage-panel, .results-heading { padding: 23px 21px; }
  .result-row { padding: 18px 21px; }
  .method { margin-top: 18px; padding: 22px; }
  .sources { padding: 35px 2px; }
  .article-layout { padding: 30px 0 42px; }
  .article-lead { font-size: 16px; }
  .article-body { margin-top: 26px; }
}

@media (max-width: 430px) {
  .brand { font-size: 17px; }
  .header-link { font-size: 13px; }
  .result-row { align-items: start; gap: 10px; }
  .model-info h3 { font-size: 15px; }
  .monthly-cost { font-size: 20px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .calculate-button { transition: none; }
}