/* ============================================================
   HK.yesletter — Apple-inspired design
   - 系统字体（macOS/iOS 自动 SF Pro）
   - 黑白底色、极少分割线、巨大留白
   - 单一品牌色：#0066cc，仅用于交互
   ============================================================ */

:root {
  --bg: #ffffff;
  --bg-soft: #fbfbfd;
  --ink: #1d1d1f;
  --ink-soft: #6e6e73;
  --ink-faint: #86868b;
  --line: #d2d2d7;
  --line-soft: #f5f5f7;
  --brand: #0066cc;
  --brand-hover: #0055aa;
  --max: 1080px;
  --pad: clamp(20px, 5vw, 48px);
}

* { box-sizing: border-box; }
html { -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
               "Helvetica Neue", Helvetica, "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 17px;
  line-height: 1.47;
  color: var(--ink);
  background: var(--bg);
  letter-spacing: -0.01em;
}

a { color: var(--brand); text-decoration: none; }
a:hover { color: var(--brand-hover); }

/* ---------- Nav ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
}
.nav-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 var(--pad);
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-brand {
  color: var(--ink);
  font-weight: 600;
  font-size: 17px;
  letter-spacing: -0.015em;
}
.nav-actions { display: flex; gap: 8px; }
.nav-btn {
  background: transparent;
  border: none;
  color: var(--ink);
  font-size: 14px;
  padding: 6px 12px;
  border-radius: 980px;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.2s;
}
.nav-btn:hover { background: rgba(0, 0, 0, 0.05); }

/* ---------- Hero ---------- */
.hero {
  padding: clamp(80px, 14vw, 160px) var(--pad) clamp(60px, 10vw, 120px);
  text-align: center;
  max-width: var(--max);
  margin: 0 auto;
}
.hero-title {
  font-size: clamp(40px, 7.2vw, 84px);
  font-weight: 600;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--ink);
  margin: 0 0 24px;
}
.hero-title .accent {
  background: linear-gradient(135deg, #0066cc 0%, #5856d6 50%, #af52de 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero-sub {
  font-size: clamp(18px, 2.2vw, 24px);
  color: var(--ink-soft);
  line-height: 1.4;
  letter-spacing: -0.012em;
  font-weight: 400;
  max-width: 680px;
  margin: 0 auto 36px;
}
.hero-cta {
  display: inline-block;
  padding: 12px 28px;
  background: var(--brand);
  color: white;
  border-radius: 980px;
  font-size: 15px;
  font-weight: 500;
  transition: background 0.2s, transform 0.2s;
}
.hero-cta:hover {
  background: var(--brand-hover);
  color: white;
  transform: translateY(-1px);
}

/* ---------- Tool / Filters ---------- */
.tool {
  background: var(--bg-soft);
  padding: clamp(60px, 9vw, 100px) var(--pad);
  border-top: 1px solid var(--line-soft);
  border-bottom: 1px solid var(--line-soft);
}
.tool-inner {
  max-width: var(--max);
  margin: 0 auto;
}
.filter-block {
  margin-bottom: 36px;
}
.filter-block:last-child { margin-bottom: 0; }

.filter-label {
  font-size: 13px;
  font-weight: 500;
  color: var(--ink-faint);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 14px;
}
.filter-label.inline { margin-bottom: 4px; }
.filter-hint {
  font-size: 13px;
  color: var(--ink-faint);
}

.pill-group {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.pill {
  display: inline-flex;
  align-items: center;
  padding: 8px 16px;
  border-radius: 980px;
  background: transparent;
  border: 1px solid var(--line);
  color: var(--ink);
  font-size: 14px;
  font-weight: 400;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.18s ease;
  letter-spacing: -0.005em;
}
.pill:hover { background: rgba(0, 0, 0, 0.04); }
.pill.active {
  background: var(--ink);
  border-color: var(--ink);
  color: white;
  font-weight: 500;
}
.pill .pill-meta {
  color: var(--ink-faint);
  font-size: 12px;
  margin-left: 6px;
}
.pill.active .pill-meta { color: rgba(255,255,255,0.6); }

/* iOS-style switch */
.filter-switch-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  background: white;
  border: 1px solid var(--line-soft);
  border-radius: 14px;
}
.switch { position: relative; display: inline-block; width: 51px; height: 31px; flex-shrink: 0; }
.switch input { opacity: 0; width: 0; height: 0; }
.switch-slider {
  position: absolute;
  inset: 0;
  background: #e5e5ea;
  border-radius: 999px;
  cursor: pointer;
  transition: background 0.25s;
}
.switch-slider::before {
  content: '';
  position: absolute;
  height: 27px;
  width: 27px;
  left: 2px;
  top: 2px;
  background: white;
  border-radius: 50%;
  box-shadow: 0 2px 4px rgba(0,0,0,0.15);
  transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.switch input:checked + .switch-slider { background: #34c759; }
.switch input:checked + .switch-slider::before { transform: translateX(20px); }

.filter-actions {
  margin-top: 28px;
  text-align: right;
}
.text-btn {
  background: none;
  border: none;
  color: var(--brand);
  font-size: 14px;
  cursor: pointer;
  font-family: inherit;
  padding: 4px 0;
}
.text-btn:hover { color: var(--brand-hover); text-decoration: underline; }

/* ---------- Results ---------- */
.results {
  padding: clamp(60px, 10vw, 120px) var(--pad);
}
.results-inner {
  max-width: var(--max);
  margin: 0 auto;
}

.results-summary {
  color: var(--ink-soft);
  font-size: 15px;
  margin-bottom: 32px;
  letter-spacing: -0.005em;
}
.results-summary:empty { display: none; }

.results-empty {
  text-align: center;
  padding: 80px 20px;
  color: var(--ink-faint);
  font-size: 18px;
  letter-spacing: -0.01em;
}
.results-empty.hidden { display: none; }

/* Compare table — Apple-style spec layout */
.results-table { overflow-x: auto; -webkit-overflow-scrolling: touch; }

table.compare {
  width: 100%;
  border-collapse: collapse;
  font-size: 15px;
  table-layout: fixed;
  min-width: 600px;
}

table.compare colgroup col.col-label { width: 160px; }
table.compare colgroup col.col-program { min-width: 240px; }

/* Program header (sticky top row) */
table.compare thead th {
  padding: 0 24px 32px;
  vertical-align: top;
  text-align: left;
  border-bottom: 1px solid var(--line);
  background: white;
  position: sticky;
  top: 48px;
  z-index: 10;
}
table.compare thead th.col-label-head { background: white; }

.program-header-card {
  padding-top: 8px;
}
.program-monogram {
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-faint);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 12px;
}
.program-name {
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.2;
  color: var(--ink);
  margin-bottom: 4px;
}
.program-name-en {
  font-size: 13px;
  color: var(--ink-faint);
  font-weight: 400;
  margin-bottom: 14px;
  letter-spacing: -0.005em;
}
.program-school {
  display: inline-block;
  font-size: 12px;
  color: var(--ink-soft);
  margin-bottom: 8px;
}
.official-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 13px;
  color: var(--brand);
  font-weight: 500;
}
.official-link:hover { text-decoration: underline; }

/* Section bands */
table.compare tr.section-row td {
  padding: 48px 24px 16px;
  font-size: 24px;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--ink);
  border-bottom: 1px solid var(--line);
  background: white;
}
table.compare tr.section-row:first-child td { padding-top: 56px; }

/* Spec rows */
table.compare tbody td {
  padding: 20px 24px;
  vertical-align: top;
  border-bottom: 1px solid var(--line-soft);
  line-height: 1.5;
  color: var(--ink);
}
table.compare tbody td.row-label {
  color: var(--ink-faint);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.02em;
  padding-top: 22px;
}

.intro-text {
  font-size: 15px;
  line-height: 1.55;
  color: var(--ink);
  letter-spacing: -0.005em;
}

.course-list {
  margin: 0;
  padding: 0;
  list-style: none;
}
.course-list li {
  padding: 4px 0;
  font-size: 14px;
  color: var(--ink);
  border-bottom: 1px solid var(--line-soft);
}
.course-list li:last-child { border-bottom: none; }

.career-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.career-tags span {
  background: var(--line-soft);
  color: var(--ink);
  padding: 4px 10px;
  border-radius: 980px;
  font-size: 13px;
  font-weight: 400;
}

.tuition-big {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.015em;
}

.meta-text {
  color: var(--ink-faint);
  font-size: 12px;
}

/* ---------- Footer ---------- */
.footer {
  background: var(--bg-soft);
  border-top: 1px solid var(--line-soft);
  padding: 40px var(--pad);
  margin-top: 60px;
}
.footer-inner {
  max-width: var(--max);
  margin: 0 auto;
  text-align: center;
}
.footer-inner p {
  margin: 0 0 8px;
  font-size: 12px;
  color: var(--ink-faint);
}
.footer-copy { color: var(--ink-faint); }

/* ---------- Toast ---------- */
.toast {
  position: fixed;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%) translateY(10px);
  background: rgba(29, 29, 31, 0.92);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  color: white;
  padding: 12px 22px;
  border-radius: 980px;
  font-size: 14px;
  font-weight: 500;
  letter-spacing: -0.005em;
  opacity: 0;
  pointer-events: none;
  transition: all 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  z-index: 100;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ---------- Print ---------- */
@media print {
  .nav, .hero, .tool, .footer, .results-summary { display: none; }
  .results { padding: 20px; }
  body { font-size: 11px; background: white; }
  table.compare thead th { position: static; padding: 0 12px 16px; }
  table.compare tbody td { padding: 10px 12px; }
  table.compare tr.section-row td { padding: 20px 12px 8px; font-size: 16px; }
  .program-name { font-size: 14px; }
}

/* ---------- Mobile ---------- */
@media (max-width: 768px) {
  .nav-inner { height: 44px; }
  .hero-title { letter-spacing: -0.02em; }
  table.compare thead th { top: 44px; }
}