/* ============================================================
   Jiahe Tang — Engineering Portfolio
   "Engineering notebook" theme: paper, grid lines, blueprint ink.
   System fonts only (perf budget); oklch accents.
   ============================================================ */

:root {
  --paper: oklch(0.975 0.006 95);
  --paper-2: oklch(0.945 0.012 95);
  --ink: oklch(0.24 0.03 250);
  --ink-soft: oklch(0.42 0.03 250);
  --muted: oklch(0.55 0.025 250);
  --line: oklch(0.82 0.02 250);
  --blue: oklch(0.52 0.17 242);
  --blue-deep: oklch(0.4 0.15 248);
  --blue-wash: oklch(0.93 0.04 240);
  --accent-red: oklch(0.55 0.19 25);
  --card: oklch(0.99 0.003 95);
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --grid: color-mix(in oklch, var(--blue) 7%, transparent);
  --grid-bold: color-mix(in oklch, var(--blue) 12%, transparent);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  font-family: var(--sans);
  color: var(--ink);
  background:
    linear-gradient(var(--grid-bold) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-bold) 1px, transparent 1px),
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px),
    var(--paper);
  background-size: 120px 120px, 120px 120px, 24px 24px, 24px 24px;
  background-position: 0 0;
  line-height: 1.6;
}

/* ------------- type ------------- */
h1, h2, h3 { line-height: 1.15; text-wrap: balance; margin: 0 0 0.5em; }
h1 { font-size: clamp(2rem, 5vw, 3.4rem); letter-spacing: -0.02em; }
h2 { font-size: clamp(1.4rem, 3vw, 2rem); }
h3 { font-size: 1.15rem; }
p { max-width: 68ch; }
a { color: var(--blue-deep); text-underline-offset: 3px; }
a:hover { color: var(--blue); }
code, .mono { font-family: var(--mono); font-size: 0.92em; }

.spec-num { font-family: var(--mono); font-variant-numeric: tabular-nums; }

.kicker {
  font-family: var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.72rem;
  color: var(--blue);
  margin: 0 0 0.6rem;
}

/* ------------- layout ------------- */
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 clamp(16px, 4vw, 40px); }

section { padding: clamp(3rem, 7vw, 5.5rem) 0; border-top: 1px solid var(--line); }
section:first-of-type { border-top: none; }

/* ------------- nav ------------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in oklch, var(--paper) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  display: flex; align-items: center; gap: 1rem; flex-wrap: wrap;
  max-width: 1200px; margin: 0 auto;
  padding: 0.65rem clamp(16px, 4vw, 40px);
}
.nav-logo {
  font-family: var(--mono); font-weight: 700; font-size: 0.95rem;
  color: var(--ink); text-decoration: none; margin-right: auto;
}
.nav-logo span { color: var(--blue); }
.nav-links { display: flex; gap: 0.25rem; flex-wrap: wrap; }
.nav-links a {
  font-family: var(--mono); font-size: 0.8rem; text-decoration: none;
  color: var(--ink-soft); padding: 0.55rem 0.8rem; border-radius: 6px;
  min-height: 44px; display: inline-flex; align-items: center;
}
.nav-links a:hover, .nav-links a:focus-visible {
  background: var(--blue-wash); color: var(--blue-deep);
}
.nav-links a[aria-current="true"] { color: var(--blue); background: var(--blue-wash); }

/* ------------- hero ------------- */
.hero { padding-top: clamp(2rem, 5vw, 4rem); }
.hero-grid {
  display: grid; gap: clamp(1.5rem, 4vw, 3rem);
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  align-items: center;
}
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; }
}
.hero h1 { margin-bottom: 0.4rem; }
.hero .tagline { font-size: clamp(1.05rem, 2vw, 1.3rem); color: var(--ink-soft); margin: 0 0 1.4rem; }
.hero-ctas { display: flex; gap: 0.75rem; flex-wrap: wrap; margin-top: 1.6rem; }

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  min-height: 44px; padding: 0.6rem 1.3rem; border-radius: 8px;
  font-family: var(--mono); font-size: 0.9rem; text-decoration: none;
  border: 1.5px solid var(--blue-deep); cursor: pointer;
}
.btn-solid { background: var(--blue-deep); color: var(--paper); }
.btn-solid:hover { background: var(--blue); border-color: var(--blue); color: var(--paper); }
.btn-ghost { background: transparent; color: var(--blue-deep); }
.btn-ghost:hover { background: var(--blue-wash); }

.hero-canvas-card {
  border: 1px solid var(--line); border-radius: 12px;
  background: var(--card);
  box-shadow: 0 1px 2px rgb(0 0 0 / 0.05), 0 8px 24px -12px oklch(0.52 0.17 242 / 0.25);
  overflow: hidden;
}
#jansen-canvas { display: block; width: 100%; height: auto; touch-action: none; cursor: grab; }
#jansen-canvas:active { cursor: grabbing; }
.canvas-controls {
  display: flex; align-items: center; gap: 0.9rem; flex-wrap: wrap;
  padding: 0.7rem 1rem; border-top: 1px solid var(--line);
  background: var(--paper-2);
  font-family: var(--mono); font-size: 0.78rem; color: var(--ink-soft);
}
.canvas-controls label { display: inline-flex; align-items: center; gap: 0.5rem; min-height: 44px; }
.canvas-controls input[type="range"] { accent-color: var(--blue); width: 130px; }
.canvas-note { color: var(--muted); font-size: 0.72rem; }

/* ------------- about ------------- */
.about-grid { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); gap: clamp(1.5rem, 4vw, 3rem); }
@media (max-width: 860px) { .about-grid { grid-template-columns: 1fr; } }
.skills-strip { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 1.4rem; padding: 0; list-style: none; }
.skills-strip li {
  font-family: var(--mono); font-size: 0.78rem;
  border: 1px solid var(--line); border-radius: 999px;
  padding: 0.45rem 0.9rem; background: var(--card);
}
.about-facts { border-left: 2px solid var(--blue); padding-left: 1.4rem; }
.about-facts dl { margin: 0; display: grid; grid-template-columns: auto 1fr; gap: 0.45rem 1rem; }
.about-facts dt { font-family: var(--mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); align-self: center; }
.about-facts dd { margin: 0; font-size: 0.95rem; }

/* ------------- projects ------------- */
.project {
  border: 1px solid var(--line); border-radius: 14px; background: var(--card);
  margin-bottom: 1.6rem; overflow: hidden;
  box-shadow: 0 1px 2px rgb(0 0 0 / 0.04);
}
.project-head {
  display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 0.5rem 1rem;
  align-items: center; padding: 1.2rem clamp(1rem, 3vw, 1.8rem);
}
.project-title { display: flex; align-items: baseline; gap: 0.7rem; flex-wrap: wrap; }
.project-title h3 { margin: 0; font-size: clamp(1.15rem, 2.4vw, 1.45rem); }
.proj-no { font-family: var(--mono); font-size: 0.75rem; color: var(--blue); }
.proj-status {
  font-family: var(--mono); font-size: 0.7rem; letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--muted); text-align: right;
}
@media (max-width: 640px) { .proj-status { text-align: left; } .project-head { grid-template-columns: 1fr; } }
.project-summary { padding: 0 clamp(1rem, 3vw, 1.8rem) 1.2rem; color: var(--ink-soft); margin: 0; }
.project-toggle {
  font-family: var(--mono); font-size: 0.82rem; color: var(--blue-deep);
  background: var(--blue-wash); border: 1px solid color-mix(in oklch, var(--blue) 30%, transparent);
  min-height: 44px; padding: 0.5rem 1.1rem; border-radius: 8px; cursor: pointer;
  margin: 0 clamp(1rem, 3vw, 1.8rem) 1.2rem; display: inline-flex; align-items: center; gap: 0.5rem;
}
.project-toggle:hover { background: color-mix(in oklch, var(--blue-wash) 70%, var(--blue) 8%); }
.project-toggle .chev { transition: transform 0.25s ease; }
.project-toggle[aria-expanded="true"] .chev { transform: rotate(180deg); }

.project-body { display: grid; grid-template-rows: 0fr; transition: grid-template-rows 0.4s ease; }
.project-body.open { grid-template-rows: 1fr; }
.project-body > div { overflow: hidden; }
.project-inner {
  padding: 0.4rem clamp(1rem, 3vw, 1.8rem) 1.6rem;
  border-top: 1px dashed var(--line);
  display: grid; gap: 1.4rem;
}
.detail-cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 1.2rem 2rem; }
.detail-cols h4 {
  font-family: var(--mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--blue); margin: 0 0 0.5rem;
}
.detail-cols p, .detail-cols ul { margin: 0 0 0.9rem; font-size: 0.95rem; }
.detail-cols ul { padding-left: 1.2rem; }
.detail-cols li { margin-bottom: 0.3rem; }

.spec-table-wrap { overflow-x: auto; }
.spec-table { border-collapse: collapse; width: 100%; font-size: 0.88rem; }
.spec-table caption { text-align: left; font-family: var(--mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); padding-bottom: 0.5rem; }
.spec-table th, .spec-table td { border: 1px solid var(--line); padding: 0.5rem 0.8rem; text-align: left; vertical-align: top; }
.spec-table th { font-family: var(--mono); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--ink-soft); background: var(--paper-2); }
.spec-table td { background: var(--card); }
.tbd { color: var(--muted); font-style: italic; }

/* galleries */
.gallery { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 0.9rem; }
figure { margin: 0; }
.asset-slot {
  border: 1.5px dashed color-mix(in oklch, var(--blue) 45%, var(--line));
  border-radius: 10px; background:
    repeating-linear-gradient(-45deg, transparent 0 10px, oklch(0.93 0.04 240 / 0.35) 10px 20px);
  min-height: 150px; display: flex; flex-direction: column; align-items: center; justify-content: center;
  gap: 0.4rem; text-align: center; aspect-ratio: 4 / 3;
}
.asset-slot .tag {
  font-family: var(--mono); font-size: 0.68rem; letter-spacing: 0.1em;
  color: var(--blue-deep); background: var(--card); border: 1px solid var(--line);
  border-radius: 4px; padding: 0.15rem 0.5rem;
}
.asset-slot figcaption { font-size: 0.78rem; color: var(--ink-soft); padding: 0 0.8rem 0.8rem; }
.gallery img { width: 100%; height: auto; border-radius: 10px; border: 1px solid var(--line); display: block; }
.gallery figcaption { font-size: 0.8rem; color: var(--muted); padding-top: 0.4rem; }

/* QDD calculator */
.calc {
  border: 1px solid var(--line); border-radius: 12px; background: var(--paper-2);
  padding: 1.2rem 1.4rem; max-width: 560px;
}
.calc h4 { margin: 0 0 0.6rem; font-family: var(--mono); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--blue); }
.calc-row { display: flex; align-items: center; gap: 0.8rem; margin: 0.55rem 0; font-size: 0.9rem; }
.calc-row label { flex: 0 0 150px; font-family: var(--mono); font-size: 0.78rem; color: var(--ink-soft); }
.calc-row input[type="range"] { flex: 1; accent-color: var(--blue); }
.calc-row output { flex: 0 0 110px; text-align: right; font-family: var(--mono); font-size: 0.85rem; }
.calc-out { margin-top: 0.9rem; border-top: 1px dashed var(--line); padding-top: 0.8rem; }
.calc-out .big { font-family: var(--mono); font-size: 1.5rem; color: var(--blue-deep); font-variant-numeric: tabular-nums; }
.calc-note { font-size: 0.75rem; color: var(--muted); margin-top: 0.6rem; }

/* ------------- skills grid ------------- */
.skills-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 1rem; list-style: none; padding: 0; margin: 0; }
.skill-card { border: 1px solid var(--line); border-radius: 10px; background: var(--card); padding: 1rem 1.1rem; }
.skill-card h3 { font-size: 0.95rem; margin: 0 0 0.3rem; font-family: var(--mono); }
.skill-card p { margin: 0; font-size: 0.85rem; color: var(--ink-soft); }
.skill-card .lvl { font-family: var(--mono); font-size: 0.7rem; color: var(--blue); letter-spacing: 0.08em; }

/* ------------- contact ------------- */
.contact-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: clamp(1.5rem, 4vw, 3rem); }
@media (max-width: 800px) { .contact-grid { grid-template-columns: 1fr; } }
.contact-list { list-style: none; padding: 0; margin: 0 0 1rem; }
.contact-list li { margin-bottom: 0.7rem; }
.contact-list a, .contact-list .unset { display: inline-flex; min-height: 44px; align-items: center; gap: 0.6rem; font-family: var(--mono); font-size: 0.9rem; }
.unset { color: var(--muted); }
.unset .todo { font-size: 0.68rem; border: 1px dashed var(--muted); border-radius: 4px; padding: 0.1rem 0.45rem; }

.contact-form { border: 1px solid var(--line); border-radius: 12px; background: var(--card); padding: 1.3rem 1.4rem; }
.contact-form label { display: block; font-family: var(--mono); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--ink-soft); margin-bottom: 0.3rem; }
.contact-form input, .contact-form textarea {
  width: 100%; font: inherit; padding: 0.6rem 0.7rem; margin-bottom: 0.9rem;
  border: 1px solid var(--line); border-radius: 8px; background: var(--paper);
}
.contact-form input:focus-visible, .contact-form textarea:focus-visible { outline: 2px solid var(--blue); outline-offset: 1px; }
.form-note { font-size: 0.75rem; color: var(--muted); margin: 0.6rem 0 0; }

/* ------------- footer ------------- */
footer { border-top: 1px solid var(--line); padding: 2rem 0 3rem; color: var(--muted); font-size: 0.82rem; }
footer .wrap { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; }

/* ------------- reveal ------------- */
.reveal { opacity: 0; transform: translateY(14px); transition: opacity 0.5s ease, transform 0.5s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  .project-body { transition: none; }
}

:focus-visible { outline: 2px solid var(--blue); outline-offset: 2px; border-radius: 4px; }