:root {
  color-scheme: light;
  --text: #202b40;
  --muted: #637086;
  --line: #e5eaf2;
  --accent: #4263df;
  --accent-dark: #3453ca;
  --page: #f6f8fc;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 28px; }
body {
  margin: 0; background: var(--page); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 14px; line-height: 1.7; -webkit-font-smoothing: antialiased;
}
h1, h2, p { margin: 0; }
a { color: inherit; text-decoration: none; }
button, input { font: inherit; }
button { cursor: pointer; }
svg.icon {
  width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 1.7;
  stroke-linecap: round; stroke-linejoin: round; flex: none;
}
a:focus-visible, button:focus-visible, summary:focus-visible {
  outline: 3px solid #8ca7ff; outline-offset: 4px; border-radius: 4px;
}
.skip-link { position: absolute; top: -60px; left: 20px; background: white; padding: 10px; z-index: 20; }
.skip-link:focus { top: 12px; }

/* A quiet header and a single, clearly defined place to begin. */
.start-header { border-bottom: 1px solid #e9edf4; background: #fff; }
.header-inner {
  width: min(1104px, calc(100% - 64px)); height: 76px; margin: auto;
  display: flex; align-items: center; justify-content: space-between; gap: 24px;
}
.start-brand { display: inline-flex; align-items: center; gap: 10px; font-size: 20px; font-weight: 650; letter-spacing: -.5px; }
.brand-mark {
  width: 34px; height: 38px; display: grid; place-items: center;
  color: white; background: var(--accent); border-radius: 10px;
}
.brand-mark .icon { width: 23px; height: 23px; }
.demo-tag {
  align-self: center; color: #64718c; background: #f0f3f8;
  padding: 2px 7px; border-radius: 5px; font-size: 11px; font-weight: 400; letter-spacing: 0;
}
.start-header nav { display: flex; align-items: center; gap: 30px; color: #566277; font-size: 13px; }
.start-header nav a:hover { color: var(--accent); }
.nav-start {
  display: inline-flex; align-items: center; gap: 7px;
  border: 1px solid #dee5f1; border-radius: 8px; padding: 7px 13px;
}
.nav-start .icon { width: 15px; height: 15px; }

.start-main { width: min(800px, calc(100% - 48px)); margin: auto; padding-top: 50px; }
.start-hero { text-align: center; }
.start-label {
  display: inline-flex; align-items: center; gap: 8px;
  color: #536bc0; font-size: 12px; line-height: 1.5; font-weight: 500;
  border: 1px solid #e2e8f8; background: #eef2fc; border-radius: 30px; padding: 6px 12px;
}
.start-label .icon { width: 14px; height: 14px; }
.start-label > span { width: 1px; height: 11px; background: #cdd6ec; margin: 0 2px; }
.start-hero h1 { font-size: 42px; font-weight: 650; letter-spacing: -1.6px; line-height: 1.5; margin-top: 15px; }
.start-hero h1 span { color: var(--accent); display: inline-block; }
.start-subtitle { color: var(--muted); font-size: 16px; line-height: 1.8; margin-top: 9px; }

.diagnosis-card {
  margin-top: 30px; padding: 28px 30px 0; background: #fff;
  border: 1px solid #e0e6f0; border-radius: 18px;
  box-shadow: 0 4px 8px #20396103, 0 16px 40px -16px #283d6a1a;
}
.card-heading { display: flex; align-items: center; gap: 13px; }
.card-symbol {
  width: 44px; height: 44px; display: grid; place-items: center; flex: none;
  color: var(--accent); border: 1px solid #e6ebfb; background: #f3f6ff; border-radius: 12px;
}
.card-symbol .icon { width: 22px; height: 22px; }
.card-heading h2 { font-size: 18px; line-height: 1.6; font-weight: 600; }
.card-heading p { color: var(--muted); font-size: 13px; margin-top: 3px; }
.start-form { margin-top: 23px; }
.role-label { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; font-size: 13px; font-weight: 500; }
.role-label span { color: #758196; font-size: 12px; font-weight: 400; }
.start-action { display: flex; gap: 12px; }
.start-input-wrap {
  display: flex; align-items: center; gap: 11px; flex: 1; min-width: 0;
  padding: 0 15px; border: 1px solid #dbe2ee; background: #fbfcfe; border-radius: 9px;
  transition: border-color .18s, box-shadow .18s;
}
.start-input-wrap:focus-within { border-color: #8ca4f5; background: #fff; box-shadow: 0 0 0 3px #4263df13; }
.start-input-wrap > .icon { color: #8696b0; }
.start-input-wrap input {
  width: 100%; min-width: 0; height: 50px; border: 0; outline: 0; padding: 0;
  background: transparent; color: var(--text); font-size: 14px;
}
.start-input-wrap input::placeholder { color: #7b889c; }
.start-submit {
  display: flex; align-items: center; justify-content: center; gap: 18px; flex: none;
  border: 1px solid var(--accent); border-radius: 9px; min-height: 52px; padding: 12px 23px;
  background: var(--accent); color: #fff; font-size: 14px; font-weight: 500;
  box-shadow: 0 3px 6px #4263df1a; transition: background .18s, box-shadow .18s;
}
.start-submit:hover { background: var(--accent-dark); box-shadow: 0 4px 12px #4263df2e; }
.start-submit:active { background: #2f49b2; }
.start-submit .icon { width: 17px; height: 17px; }
.start-roles { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin-top: 12px; }
.start-roles > span { color: #758196; font-size: 12px; margin-right: 3px; }
.start-roles button {
  color: #5e6c82; background: #f5f7fb; border: 1px solid transparent; border-radius: 6px;
  padding: 5px 10px; min-height: 32px; font-size: 12px; line-height: 1.6;
  transition: background .15s, color .15s, border-color .15s;
}
.start-roles button:hover, .start-roles button[aria-pressed="true"] { color: var(--accent-dark); border-color: #d7e0fc; background: #edf2ff; }
.card-footer {
  display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 12px;
  margin-top: 23px; padding: 16px 0; border-top: 1px solid #edf0f5; color: var(--muted); font-size: 12px;
}
.card-footer p, .card-footer a { display: flex; align-items: center; gap: 7px; }
.card-footer .icon { width: 15px; height: 15px; }
.card-footer a { color: #556b9a; }
.card-footer a:hover { color: var(--accent); }

.start-features {
  display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 18px;
  list-style: none; padding: 0 4px; margin: 30px 0 0;
}
.start-features li { display: flex; align-items: flex-start; gap: 11px; }
.feature-symbol { color: #627dae; display: grid; place-items: center; margin-top: 3px; }
.feature-symbol .icon { width: 19px; height: 19px; }
.start-features h2 { font-size: 14px; font-weight: 550; line-height: 1.7; }
.start-features p { margin-top: 4px; color: var(--muted); font-size: 12px; line-height: 1.8; }

.start-help { margin-top: 44px; }
.help-heading { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin-bottom: 14px; }
.help-heading h2 { font-size: 16px; font-weight: 600; }
.help-heading > span { font-size: 12px; color: #748196; }
.help-list { border: 1px solid var(--line); border-radius: 12px; background: #ffffffa6; padding: 0 22px; }
.start-help details + details { border-top: 1px solid var(--line); }
.start-help summary {
  list-style: none; cursor: pointer; display: flex; align-items: center; justify-content: space-between;
  gap: 20px; padding: 17px 0; color: #4d5b71; font-size: 14px; line-height: 1.7;
}
.start-help summary::-webkit-details-marker { display: none; }
.start-help summary:hover { color: var(--accent); }
.start-help summary .icon { width: 16px; height: 16px; color: #7d8ca3; transition: transform .18s; }
.start-help details[open] summary { color: var(--accent-dark); }
.start-help details[open] summary .icon { transform: rotate(45deg); }
.help-content { padding: 0 0 19px; color: var(--muted); font-size: 13px; line-height: 1.9; }
.help-content > p + p { margin-top: 12px; }
.help-content strong { color: #3e4c64; font-weight: 550; }
.help-content dl { margin: 0; }
.help-content dl > div { display: grid; grid-template-columns: 70px minmax(0, 1fr); gap: 15px; margin-bottom: 10px; }
.help-content dt { color: #3e4c64; font-weight: 500; }
.help-content dd { margin: 0; }
.help-content .help-note { font-size: 12px; color: #718095; margin-top: 12px; }
.rewrite-example { padding: 12px 15px; background: #f1f4f8; border-radius: 8px; }
.rewrite-example + .rewrite-example { margin-top: 10px; }
.rewrite-example > span { color: #64748b; font-size: 11px; font-weight: 600; }
.rewrite-example p { margin-top: 4px; }
.rewrite-example.improved { background: #edf2ff; }
.rewrite-example.improved > span { color: var(--accent); }
.demo-note { display: flex; align-items: center; justify-content: center; gap: 6px; margin-top: 22px; color: #728096; font-size: 12px; }
.demo-note .icon { width: 14px; height: 14px; }
.start-footer {
  width: min(800px, calc(100% - 48px)); margin: 27px auto 0; padding: 0 0 28px;
  display: flex; align-items: center; justify-content: space-between; gap: 20px; color: #718095; font-size: 12px;
}
.footer-divider { margin: 0 12px; color: #b9c3d2; }
.start-footer a { display: inline-flex; align-items: center; gap: 6px; }
.start-footer a:hover { color: var(--accent); }
.start-footer .icon { width: 14px; height: 14px; }

@media (min-width: 1500px) {
  .start-main { padding-top: 64px; }
}
@media (max-width: 760px) {
  .header-inner { width: calc(100% - 40px); height: 70px; gap: 16px; }
  .start-brand { font-size: 19px; gap: 8px; }
  .brand-mark { width: 31px; height: 35px; border-radius: 9px; }
  .brand-mark .icon { width: 21px; height: 21px; }
  .start-header nav { gap: 18px; font-size: 12px; }
  .nav-start { display: none; }
  .start-main { max-width: 600px; padding-top: 38px; }
  .start-hero h1 { font-size: 34px; letter-spacing: -1px; }
  .start-subtitle { font-size: 14px; }
  .diagnosis-card { padding: 23px 24px 0; border-radius: 16px; margin-top: 27px; }
  .card-heading h2 { font-size: 17px; }
  .start-input-wrap { padding-inline: 12px; gap: 9px; }
  .start-input-wrap input { font-size: 16px; }
  .start-input-wrap input::placeholder { font-size: 13px; }
  .start-submit { padding-inline: 18px; gap: 12px; }
  .start-roles { gap: 6px; }
  .start-features { gap: 15px; }
  .start-features li { display: block; }
  .feature-symbol { width: 22px; height: 22px; margin: 0 0 7px; }
  .start-features h2 { font-size: 13px; }
  .start-features p { font-size: 12px; }
  .help-heading > span { display: none; }
  .start-help { margin-top: 34px; }
  .start-footer { max-width: 600px; }
}
@media (max-width: 480px) {
  .header-inner { width: calc(100% - 36px); height: 66px; }
  .start-header nav a:first-child { display: none; }
  .start-brand { font-size: 18px; }
  .demo-tag { font-size: 10px; padding-inline: 5px; }
  .start-main { width: calc(100% - 36px); padding-top: 34px; }
  .start-label { font-size: 11px; padding: 5px 10px; }
  .start-hero h1 { max-width: 300px; margin: 15px auto 0; font-size: 32px; line-height: 1.4; letter-spacing: -.8px; }
  .start-hero h1 span { display: block; }
  .start-subtitle { max-width: 290px; margin: 12px auto 0; font-size: 13px; line-height: 1.9; text-wrap: balance; }
  .diagnosis-card { padding: 21px 19px 0; margin-top: 24px; border-radius: 14px; }
  .card-heading { gap: 11px; }
  .card-symbol { width: 39px; height: 42px; border-radius: 10px; }
  .card-symbol .icon { width: 21px; height: 21px; }
  .card-heading h2 { font-size: 16px; }
  .card-heading p { font-size: 12px; }
  .start-form { margin-top: 20px; }
  .start-action { flex-direction: column; gap: 11px; }
  .start-submit { min-height: 48px; width: 100%; }
  .start-input-wrap input { height: 48px; }
  .start-roles { gap: 6px; margin-top: 13px; }
  .start-roles > span { display: none; }
  .start-roles button { font-size: 11px; min-height: 34px; padding: 5px 8px; }
  .card-footer { margin-top: 18px; padding-block: 14px; gap: 9px; font-size: 11px; justify-content: center; }
  .card-footer p { width: 100%; justify-content: center; }
  .start-features { gap: 13px; margin-top: 25px; padding-inline: 2px; }
  .start-features h2 { font-size: 12px; }
  .start-features p { font-size: 11px; line-height: 1.85; }
  .feature-symbol .icon { width: 18px; height: 18px; }
  .help-heading h2 { font-size: 15px; }
  .help-list { padding-inline: 16px; border-radius: 10px; }
  .start-help summary { font-size: 13px; gap: 12px; padding-block: 16px; }
  .help-content { font-size: 12px; }
  .help-content dl > div { grid-template-columns: 60px minmax(0, 1fr); gap: 10px; }
  .start-footer { width: calc(100% - 36px); flex-direction: column; gap: 9px; margin-top: 24px; font-size: 11px; }
  .demo-note { font-size: 11px; }
}
@media (max-width: 350px) {
  .start-hero h1 { font-size: 29px; }
  .diagnosis-card { padding-inline: 15px; }
  .start-roles { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .start-roles button { font-size: 12px; }
  .start-features { gap: 10px; }
  .start-features h2 { font-size: 11px; }
  .card-heading p { font-size: 11px; }
}
@media (prefers-reduced-motion: reduce) {
  *, html { transition: none !important; scroll-behavior: auto !important; }
}