/* AI 上手实验室 — Apple design system (2026-08) */
:root {
  --bg: #f5f5f7;
  --bg-elevated: #ffffff;
  --bg-soft: #ebebed;
  --fg: #1d1d1f;
  --fg-2: #3a3a3c;
  --muted: #6e6e73;
  --meta: #86868b;
  --border: rgba(0, 0, 0, 0.08);
  --border-strong: rgba(0, 0, 0, 0.16);
  --accent: #0071e3;
  --accent-hover: #0077ed;
  --accent-soft: rgba(0, 113, 227, 0.08);
  --accent-alt: #1d1d1f;
  --accent-alt-soft: rgba(29, 29, 31, 0.05);
  --danger: #ff3b30;
  --danger-soft: rgba(255, 59, 48, 0.08);
  --warn: #bf4800;
  --warn-soft: rgba(191, 72, 0, 0.08);
  --ok: #34c759;
  --ok-soft: rgba(52, 199, 89, 0.10);
  --term-bg: #1d1d1f;
  --term-fg: #f5f5f7;
  --diff-del: #ffe5e3;
  --diff-add: #e3f6e5;
  --font-display: -apple-system, BlinkMacSystemFont, "SF Pro Display", "PingFang SC", "Helvetica Neue", "Microsoft YaHei", sans-serif;
  --font-body: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Helvetica Neue", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;
  --container: 1024px;
  --teach: 720px;
  --side: 300px;
  --rail: 200px;
  --gutter: 24px;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.03), 0 12px 32px rgba(0, 0, 0, 0.08);
  --focus: 0 0 0 4px rgba(0, 113, 227, 0.32);
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--fg);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.65;
  background-color: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; cursor: pointer; border: 0; background: none; color: inherit; }
p { margin: 0; text-wrap: pretty; }
h1, h2, h3, h4 { margin: 0; text-wrap: balance; font-weight: 600; letter-spacing: -0.022em; line-height: 1.15; }
code, kbd, pre { font-family: var(--font-mono); }

.container { max-width: var(--container); margin-inline: auto; padding-inline: var(--gutter); }
.muted { color: var(--muted); }
.meta {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--meta);
  letter-spacing: 0.02em;
}
.eyebrow {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 14px;
}
.lead {
  color: var(--muted);
  font-size: 18px;
  line-height: 1.55;
  max-width: 46ch;
}
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}

/* Nav — translucent glass, Apple-style */
.topnav {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(245, 245, 247, 0.82);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border);
}
.topnav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 56px;
  padding-block: 8px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  letter-spacing: -0.022em;
  white-space: nowrap;
}
.brand-mark {
  width: 28px; height: 28px;
  border-radius: 7px;
  background: var(--fg);
  color: #fff;
  display: grid; place-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
}
.brand small { color: var(--muted); font-weight: 400; font-size: 13px; margin-left: 4px; }
.nav-links {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-wrap: wrap;
  justify-content: flex-end;
}
.nav-links a {
  font-size: 14px;
  color: var(--muted);
  padding: 10px 12px;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  border-radius: 980px;
  transition: color .15s ease, background .15s ease;
}
.nav-links a:hover,
.nav-links a.is-active {
  color: var(--fg);
  background: rgba(0, 0, 0, 0.05);
}
.nav-links a.is-active { font-weight: 500; }

/* Keyboard focus: every interactive element gets a visible ring */
a:focus-visible,
button:focus-visible,
[role="tab"]:focus-visible,
[role="button"]:focus-visible,
[tabindex]:focus-visible {
  outline: none;
  box-shadow: var(--focus);
}

/* Buttons — Apple pill + filled CTA */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: 980px;
  border: 1px solid transparent;
  font-size: 15px;
  font-weight: 500;
  transition: transform .15s ease, background .15s ease, border-color .15s ease, box-shadow .15s ease;
}
.btn:focus-visible { outline: none; box-shadow: var(--focus); }
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn-primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn-secondary {
  background: var(--bg-elevated);
  color: var(--fg);
  border-color: var(--border-strong);
}
.btn-secondary:hover { border-color: var(--fg); }
.btn-ghost {
  color: var(--muted);
  padding-inline: 12px;
}
.btn-ghost:hover { color: var(--fg); }
.btn-block { width: 100%; }
.btn-sm { padding: 8px 16px; font-size: 13px; }

/* Cards / surfaces */
.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}
.soft-panel {
  background: rgba(0, 0, 0, 0.03);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
}

/* Home */
.hero {
  padding: clamp(48px, 8vw, 96px) 0 clamp(36px, 5vw, 64px);
}
.hero-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 40px;
  align-items: start;
}
.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(32px, 5vw, 48px);
  line-height: 1.12;
  letter-spacing: -0.025em;
  margin-bottom: 18px;
  max-width: 14ch;
}
.hero .lead { margin-bottom: 22px; }
.loop {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 20px 0 28px;
}
.loop span {
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 6px 10px;
  border-radius: 980px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--fg-2);
}
.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin-bottom: 18px;
}
.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 20px;
  color: var(--muted);
  font-size: 14px;
}
.hero-meta strong { color: var(--fg); font-weight: 500; }
.safety-card h2 {
  font-size: 16px;
  margin-bottom: 12px;
}
.safety-card ul {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
}
.safety-card li {
  display: flex;
  gap: 10px;
  font-size: 14px;
  color: var(--fg-2);
  line-height: 1.45;
}
.safety-card li::before {
  content: "✓";
  color: var(--ok);
  font-weight: 600;
  flex: 0 0 auto;
}
.secondary-entries {
  padding: 0 0 64px;
}
.entry-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.entry-card {
  display: block;
  text-align: left;
  padding: 22px 22px 20px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  transition: border-color .15s ease, transform .15s ease, box-shadow .15s ease;
}
.entry-card:hover {
  border-color: var(--border-strong);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}
.entry-card .k {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--meta);
  margin-bottom: 8px;
}
.entry-card h3 { font-size: 18px; margin-bottom: 6px; }
.entry-card p { color: var(--muted); font-size: 14px; }
.unlock {
  margin-top: 28px;
  padding: 20px 22px;
  border-radius: var(--radius);
  border: 1px dashed var(--border-strong);
  background: var(--accent-alt-soft);
}
.unlock h3 { font-size: 15px; margin-bottom: 10px; color: var(--fg); }
.unlock ul {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
  font-size: 14px;
  display: grid;
  gap: 4px;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 40px 0 48px;
  margin-top: 24px;
  color: var(--muted);
  font-size: 13px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 24px;
}
.site-footer h4 {
  font-size: 12px;
  font-family: var(--font-mono);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--meta);
  margin-bottom: 10px;
}
.site-footer a { color: var(--fg-2); }
.site-footer a:hover { color: var(--accent); }
.site-footer ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.footer-note { margin-top: 28px; padding-top: 18px; border-top: 1px solid var(--border); }

/* Lab shell */
.lab-shell {
  display: grid;
  grid-template-columns: var(--rail) minmax(0, 1fr) var(--side);
  gap: 20px;
  padding: 20px 0 56px;
  align-items: start;
}
.lab-header {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  padding-bottom: 8px;
}
.lab-header h1 {
  font-size: 18px;
  font-weight: 600;
}
.progress-pill {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 980px;
  padding: 6px 12px;
}
.progress-pill .dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--ok);
  box-shadow: 0 0 0 3px var(--ok-soft);
}
.step-rail {
  position: sticky;
  top: 76px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 12px;
}
.step-rail ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 4px;
}
.step-rail button {
  width: 100%;
  text-align: left;
  display: flex;
  gap: 8px;
  align-items: flex-start;
  padding: 8px 8px;
  border-radius: 8px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.35;
}
.step-rail button:hover { background: rgba(0, 0, 0, 0.04); color: var(--fg); }
.step-rail button.is-active {
  background: var(--accent-soft);
  color: var(--fg);
  font-weight: 500;
}
.step-rail button.is-done { color: var(--ok); }
.step-rail button.is-locked,
.step-rail button[disabled] {
  opacity: 0.45;
  cursor: not-allowed;
}
.step-rail button.is-locked:hover,
.step-rail button[disabled]:hover {
  background: transparent;
  color: var(--muted);
}
.step-rail .n {
  font-family: var(--font-mono);
  font-size: 11px;
  width: 18px;
  flex: 0 0 auto;
  opacity: 0.8;
}
.teach {
  min-width: 0;
}
.teach-panel {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: clamp(20px, 3vw, 32px);
  box-shadow: var(--shadow);
  min-height: 480px;
}
.teach-panel h2 {
  font-size: clamp(22px, 3vw, 28px);
  line-height: 1.22;
  letter-spacing: -0.02em;
  margin-bottom: 10px;
}
.teach-panel .sub {
  color: var(--muted);
  margin-bottom: 22px;
  max-width: 52ch;
}
.side-panel {
  position: sticky;
  top: 76px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
}
.side-panel h3 {
  font-size: 13px;
  font-family: var(--font-mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--meta);
  margin-bottom: 12px;
}
.perm-list {
  display: grid;
  gap: 10px;
  font-size: 13px;
}
.perm-row {
  display: grid;
  grid-template-columns: 64px 1fr;
  gap: 8px;
  align-items: start;
}
.perm-row .k { color: var(--meta); }
.perm-row .v { color: var(--fg-2); line-height: 1.4; }
.risk-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 4px 8px;
  border-radius: 980px;
  border: 1px solid var(--border);
}
.risk-view { background: var(--ok-soft); color: var(--ok); border-color: transparent; }
.risk-edit { background: var(--warn-soft); color: var(--warn); border-color: transparent; }
.risk-net { background: var(--accent-soft); color: var(--accent); border-color: transparent; }
.risk-high { background: var(--danger-soft); color: var(--danger); border-color: transparent; }

/* Wizard choices */
.choice-grid {
  display: grid;
  gap: 10px;
}
.choice {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  width: 100%;
  text-align: left;
  padding: 14px 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg);
  transition: border-color .15s ease, background .15s ease, box-shadow .15s ease;
}
.choice:hover {
  border-color: var(--border-strong);
  background: var(--bg-elevated);
}
.choice.is-selected {
  border-color: var(--accent);
  background: var(--accent-soft);
  box-shadow: inset 0 0 0 1px rgba(0, 113, 227, 0.25);
}
.choice .mark {
  width: 22px; height: 22px;
  border-radius: 50%;
  border: 1.5px solid var(--border-strong);
  display: grid; place-items: center;
  flex: 0 0 auto;
  margin-top: 1px;
  font-size: 12px;
  color: transparent;
}
.choice.is-selected .mark {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.choice strong {
  display: block;
  font-size: 15px;
  margin-bottom: 2px;
}
.choice small {
  display: block;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.45;
}
.hint-box {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: 10px;
  background: var(--accent-alt-soft);
  color: var(--fg-2);
  font-size: 14px;
  display: none;
}
.hint-box.is-open { display: block; }
.rec-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px;
  background: var(--bg-elevated);
}
.rec-card h3 { font-size: 18px; margin: 6px 0 10px; }
.rec-card ul {
  margin: 0 0 16px;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 6px;
  font-size: 14px;
  color: var(--fg-2);
}
.rec-card li::before { content: "✓ "; color: var(--ok); }
.actions-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 22px;
}

/* Command card */
.cmd-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  background: var(--bg-elevated);
  margin: 16px 0;
}
.cmd-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 14px;
  padding: 12px 14px;
  border-bottom: 1px solid var(--border);
  font-size: 12px;
  color: var(--muted);
}
.cmd-meta strong { color: var(--fg-2); font-weight: 500; }
.cmd-body {
  background: var(--term-bg);
  color: var(--term-fg);
  padding: 14px 16px;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}
.cmd-body pre {
  margin: 0;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: 13px;
  line-height: 1.5;
  flex: 1;
}
.cmd-copy {
  flex: 0 0 auto;
  color: var(--fg);
  background: var(--term-fg);
  border-radius: 8px;
  padding: 6px 10px;
  font-size: 12px;
  font-weight: 500;
}
.cmd-copy.is-done { background: var(--ok); color: #fff; }
.cmd-help {
  padding: 14px 16px;
  font-size: 14px;
  color: var(--fg-2);
  display: grid;
  gap: 8px;
}
.cmd-help .label { color: var(--meta); font-size: 12px; font-family: var(--font-mono); }

/* Prompt / diff */
.prompt-box, .diff-box {
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  margin: 14px 0;
}
.prompt-box header, .diff-box header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 14px;
  background: rgba(0, 0, 0, 0.03);
  border-bottom: 1px solid var(--border);
  font-size: 12px;
  font-family: var(--font-mono);
  color: var(--meta);
}
.prompt-box pre, .diff-box pre {
  margin: 0;
  padding: 14px 16px;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: 13px;
  line-height: 1.55;
  background: var(--bg-elevated);
}
.diff-box .del { background: var(--diff-del); color: var(--danger); display: block; padding: 2px 6px; margin: 0 -6px; border-radius: 4px; }
.diff-box .add { background: var(--diff-add); color: var(--ok); display: block; padding: 2px 6px; margin: 0 -6px; border-radius: 4px; }
.check-list {
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 6px;
  font-size: 14px;
}
.check-list li::before { content: "✓ "; color: var(--ok); }
.stop-list {
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 6px;
  font-size: 14px;
  color: var(--danger);
}
.stop-list li::before { content: "× "; }

/* Branch buttons */
.branch-grid {
  display: grid;
  gap: 8px;
  margin-top: 16px;
}
.branch-btn {
  text-align: left;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  font-size: 14px;
}
.branch-btn:hover { border-color: var(--border-strong); background: var(--bg); }
.branch-btn.ok { border-color: color-mix(in srgb, var(--ok) 35%, var(--border)); }
.branch-panel {
  display: none;
  margin-top: 14px;
  padding: 14px;
  border-radius: 10px;
  background: var(--warn-soft);
  border: 1px solid color-mix(in srgb, var(--warn) 25%, transparent);
  font-size: 14px;
  color: var(--fg-2);
}
.branch-panel.is-open { display: block; }

/* Concept pop */
.concept {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  border-bottom: 1px dashed color-mix(in srgb, var(--accent) 50%, transparent);
  color: var(--fg);
  cursor: help;
  font-weight: 500;
}
.concept-pop {
  display: none;
  margin: 12px 0;
  padding: 12px 14px;
  border-radius: 10px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  font-size: 14px;
  color: var(--fg-2);
}
.concept-pop.is-open { display: block; }
.concept-pop strong { display: block; margin-bottom: 4px; color: var(--fg); }

/* Simple content pages */
.page-hero {
  padding: 48px 0 28px;
}
.page-hero h1 {
  font-family: var(--font-display);
  font-size: clamp(28px, 4vw, 40px);
  letter-spacing: -0.025em;
  margin-bottom: 12px;
}
.content {
  max-width: 720px;
  padding-bottom: 64px;
}
.content h2 {
  font-size: 22px;
  margin: 28px 0 10px;
}
.content p + p { margin-top: 12px; }
.content ul { padding-left: 18px; color: var(--fg-2); }
.content li + li { margin-top: 6px; }

/* Practice preview */
.preview-frame {
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  background: #fff;
  margin: 14px 0;
}
.preview-frame iframe {
  width: 100%;
  height: 180px;
  border: 0;
  display: block;
}

/* Hidden steps */
.step-view[hidden] { display: none !important; }

/* Utility classes: keep one-off sizing out of the markup */
.text-sm { font-size: 14px; }
.fg-2 { color: var(--fg-2); }
.mt-0 { margin-top: 0; }
.mt-16 { margin-top: 16px; }
.mb-8 { margin-bottom: 8px; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 16px 0; }
.footer-note-flush { margin-top: 0; padding-top: 0; border-top: 0; }
@media (max-width: 560px) { .grid-2 { grid-template-columns: 1fr; } }

@media (max-width: 980px) {
  .lab-shell {
    grid-template-columns: 1fr;
  }
  .step-rail, .side-panel {
    position: static;
  }
  .step-rail ol {
    display: flex;
    overflow-x: auto;
    gap: 4px;
  }
  .step-rail button {
    min-width: 120px;
    white-space: nowrap;
  }
  .hero-grid, .entry-grid, .footer-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .topnav-inner { flex-wrap: wrap; row-gap: 4px; }
  .nav-links { width: 100%; order: 2; overflow-x: auto; flex-wrap: nowrap; justify-content: flex-start; -webkit-overflow-scrolling: touch; scrollbar-width: none; }
  .nav-links::-webkit-scrollbar { display: none; }
  .nav-links a { white-space: nowrap; flex: 0 0 auto; }
  .hero h1 { max-width: none; }
}