/* Engineering Learning Hub — dashboard + viewer chrome.
   Artifacts render inside an iframe, so nothing here reaches them. */

:root {
  --bg: #f6f6f3;
  --surface: #ffffff;
  --surface-2: #efefeb;
  --border: #e2e2dc;
  --border-strong: #cfcfc7;
  --text: #1b1b19;
  --muted: #6a6a63;
  --accent: #3451d1;
  --accent-soft: #e8ecfd;
  --star: #d99a0b;
  --danger: #b4321f;
  --shadow: 0 1px 2px rgba(20, 20, 15, .04), 0 4px 16px rgba(20, 20, 15, .05);
  --shadow-hover: 0 2px 4px rgba(20, 20, 15, .06), 0 10px 28px rgba(20, 20, 15, .09);
  --radius: 14px;
  --font: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1014;
    --surface: #161920;
    --surface-2: #1e222b;
    --border: #272c36;
    --border-strong: #363c49;
    --text: #e7e8ec;
    --muted: #949aa6;
    --accent: #8299ff;
    --accent-soft: #1d2444;
    --star: #f2b42c;
    --danger: #f07a66;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3);
    --shadow-hover: 0 2px 6px rgba(0, 0, 0, .35), 0 10px 28px rgba(0, 0, 0, .35);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #0e1014;
  --surface: #161920;
  --surface-2: #1e222b;
  --border: #272c36;
  --border-strong: #363c49;
  --text: #e7e8ec;
  --muted: #949aa6;
  --accent: #8299ff;
  --accent-soft: #1d2444;
  --star: #f2b42c;
  --danger: #f07a66;
  --shadow: 0 1px 2px rgba(0, 0, 0, .3);
  --shadow-hover: 0 2px 6px rgba(0, 0, 0, .35), 0 10px 28px rgba(0, 0, 0, .35);
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }

html, body { margin: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 var(--font);
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; }
button { font: inherit; color: inherit; }

.wrap {
  max-width: 1120px;
  margin: 0 auto;
  padding: 40px 20px 80px;
}

/* ---------- Header ---------- */
.hub-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 24px;
}
.hub-title {
  margin: 0;
  font-size: clamp(26px, 4vw, 34px);
  font-weight: 700;
  letter-spacing: -.02em;
}
.hub-sub { margin: 4px 0 0; color: var(--muted); }

.icon-btn {
  display: inline-grid;
  place-items: center;
  width: 36px;
  height: 36px;
  flex: none;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
  cursor: pointer;
  text-decoration: none;
  transition: border-color .15s, background .15s;
}
.icon-btn:hover { border-color: var(--border-strong); background: var(--surface-2); }
.icon-btn svg { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.icon-btn[aria-pressed="true"] svg { fill: var(--star); stroke: var(--star); }

/* ---------- Search ---------- */
.search {
  position: relative;
  display: flex;
  align-items: center;
  margin-bottom: 28px;
}
.search svg {
  position: absolute;
  left: 14px;
  width: 18px;
  height: 18px;
  fill: none;
  stroke: var(--muted);
  stroke-width: 2;
  stroke-linecap: round;
  pointer-events: none;
}
.search input {
  width: 100%;
  padding: 13px 48px 13px 42px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-size: 16px;
  box-shadow: var(--shadow);
  outline: none;
  transition: border-color .15s, box-shadow .15s;
}
.search input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.search input::-webkit-search-cancel-button { display: none; }
.search kbd {
  position: absolute;
  right: 12px;
  padding: 1px 7px;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--muted);
  font: 12px var(--mono);
}

/* ---------- Continue learning ---------- */
.continue {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-bottom: 28px;
  padding: 20px 22px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: linear-gradient(135deg, var(--accent-soft), var(--surface) 70%);
  box-shadow: var(--shadow);
}
.continue-body { flex: 1; min-width: 0; }
.continue-kicker {
  margin: 0 0 2px;
  color: var(--accent);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: .06em;
  text-transform: uppercase;
}
.continue-title { margin: 0; font-size: 20px; font-weight: 650; }
.continue-meta { margin: 2px 0 0; color: var(--muted); font-size: 13px; }
.continue .progress { max-width: 320px; margin-top: 10px; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  flex: none;
  padding: 10px 16px;
  border: 0;
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
}
.btn:hover { filter: brightness(1.08); }
:root[data-theme="dark"] .btn { color: #0e1014; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .btn { color: #0e1014; } }

/* ---------- Recent ---------- */
.recent { margin-bottom: 28px; }
.section-label {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: .06em;
  text-transform: uppercase;
}
.recent-list { display: flex; flex-wrap: wrap; gap: 8px; }
.recent-chip {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  padding: 7px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  font-size: 14px;
  text-decoration: none;
  transition: border-color .15s;
}
.recent-chip:hover { border-color: var(--accent); }
.recent-chip small { color: var(--muted); font-size: 12px; }

/* ---------- Filters ---------- */
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 8px;
}
.filter {
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  font-size: 14px;
  cursor: pointer;
  transition: all .15s;
}
.filter:hover { color: var(--text); border-color: var(--border-strong); }
.filter[aria-pressed="true"] {
  border-color: var(--text);
  background: var(--text);
  color: var(--bg);
}
.filter .count { margin-left: 4px; opacity: .6; font-size: 12px; }

/* ---------- Catalog ---------- */
.category { margin-top: 32px; }
.category-title {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin: 0 0 14px;
  font-size: 18px;
  font-weight: 650;
}
.category-title span { color: var(--muted); font-size: 13px; font-weight: 500; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
  gap: 16px;
}

.card {
  position: relative;
  display: flex;
  flex-direction: column;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
  transition: transform .15s, box-shadow .15s, border-color .15s;
}
.card:hover { transform: translateY(-2px); box-shadow: var(--shadow-hover); border-color: var(--border-strong); }
.card:focus-within { border-color: var(--accent); }

.card-head { display: flex; align-items: flex-start; gap: 10px; }
.card-title { flex: 1; margin: 0; font-size: 17px; font-weight: 650; line-height: 1.3; }
.card-title a { text-decoration: none; outline: none; }
/* Whole card is clickable via the title link; star button sits above it. */
.card-title a::after { content: ""; position: absolute; inset: 0; border-radius: var(--radius); }
.card .icon-btn { position: relative; z-index: 1; width: 32px; height: 32px; border-color: transparent; background: transparent; }
.card .icon-btn:hover { background: var(--surface-2); }

.card-desc { margin: 6px 0 0; color: var(--muted); font-size: 14px; }

.card-points {
  margin: 14px 0 0;
  padding: 0;
  list-style: none;
  font-size: 14px;
}
.card-points li { position: relative; padding: 2px 0 2px 16px; }
.card-points li::before {
  content: "";
  position: absolute;
  left: 2px;
  top: .72em;
  width: 6px;
  height: 6px;
  border-radius: 2px;
  background: var(--accent);
  opacity: .7;
}

.tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 14px; }
.tag {
  padding: 2px 8px;
  border-radius: 6px;
  background: var(--surface-2);
  color: var(--muted);
  font-size: 12px;
}

.card-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: auto;
  padding-top: 18px;
}
.card-open { color: var(--accent); font-size: 14px; font-weight: 600; white-space: nowrap; }
.card:hover .card-open { text-decoration: underline; text-underline-offset: 3px; }
.card-foot .progress { flex: 1; max-width: 140px; }

.badge-missing {
  display: inline-block;
  margin-top: 12px;
  padding: 3px 8px;
  border: 1px dashed var(--danger);
  border-radius: 6px;
  color: var(--danger);
  font: 12px var(--mono);
  align-self: flex-start;
}

.progress {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  font-size: 12px;
}
.progress-track {
  flex: 1;
  height: 4px;
  border-radius: 99px;
  background: var(--surface-2);
  overflow: hidden;
}
.progress-fill { height: 100%; border-radius: inherit; background: var(--accent); }

mark { background: var(--accent-soft); color: inherit; border-radius: 3px; padding: 0 1px; }

.empty {
  margin: 48px 0;
  color: var(--muted);
  text-align: center;
}
.empty code, .viewer-msg code {
  padding: 1px 6px;
  border-radius: 5px;
  background: var(--surface-2);
  font: 13px var(--mono);
}

@media (max-width: 560px) {
  .wrap { padding-top: 24px; }
  .continue { flex-direction: column; align-items: stretch; }
  .continue .btn { justify-content: center; }
  .search kbd { display: none; }
}

/* ================= Viewer ================= */
body.viewer {
  display: flex;
  flex-direction: column;
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
}

.vbar {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: none;
  height: 52px;
  padding: 0 12px;
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}

.vbar-back {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  flex: none;
  padding: 6px 10px;
  border-radius: 8px;
  color: var(--muted);
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
}
.vbar-back:hover { background: var(--surface-2); color: var(--text); }

.vbar-title {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 10px;
  flex: 1;
  min-width: 0;
}
.vbar-title h1 {
  margin: 0;
  overflow: hidden;
  font-size: 15px;
  font-weight: 650;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.vbar-cat { flex: none; color: var(--muted); font-size: 12px; }

.vbar-actions { display: flex; align-items: center; gap: 6px; flex: none; }
.vbar .icon-btn { width: 34px; height: 34px; }

.nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  height: 34px;
  max-width: 220px;
  padding: 0 12px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
  font-size: 13px;
  text-decoration: none;
  white-space: nowrap;
}
.nav-btn span:not([aria-hidden]) { overflow: hidden; text-overflow: ellipsis; }
.nav-btn:hover { border-color: var(--border-strong); background: var(--surface-2); }
.nav-btn[aria-disabled="true"] { opacity: .4; pointer-events: none; }

.vframe { position: relative; flex: 1; min-height: 0; }
.vframe iframe {
  display: block;
  width: 100%;
  height: 100%;
  border: 0;
  /* Same default a browser gives a standalone page, so the artifact looks exactly as when opened directly. */
  background: #fff;
}

.viewer-msg {
  position: absolute;
  inset: 0;
  display: grid;
  place-content: center;
  gap: 8px;
  padding: 24px;
  background: var(--bg);
  color: var(--muted);
  text-align: center;
}
.viewer-msg strong { color: var(--text); font-size: 18px; }

@media (max-width: 860px) { .hide-md { display: none; } .vbar-cat { display: none; } }
@media (max-width: 520px) {
  .hide-sm { display: none; }
  .vbar { gap: 6px; padding: 0 8px; }
  .vbar-title { justify-content: flex-start; }
  .nav-btn { padding: 0 10px; }
}