/* chemistry.gtdigital.tech — base styles */
:root {
  --bg: #0b1020;
  --bg-soft: #131a30;
  --card: #1a223e;
  --line: #2a3358;
  --ink: #e8ecff;
  --ink-dim: #aab2d5;
  --accent: #7dd3fc;      /* sky-300 */
  --accent-2: #c084fc;    /* purple-400 */
  --good: #4ade80;
  --bad: #f87171;
  --warn: #fbbf24;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, sans-serif;
  background: radial-gradient(1200px 600px at 10% -10%, #1e2a5e 0%, var(--bg) 60%) fixed;
  color: var(--ink);
  min-height: 100vh;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3 { font-weight: 700; line-height: 1.2; margin: 0 0 .5em; }
h1 { font-size: 2rem; }
h2 { font-size: 1.4rem; color: var(--accent); }
h3 { font-size: 1.1rem; color: var(--accent-2); }
code, pre { font-family: "JetBrains Mono", "Cascadia Code", Consolas, monospace; }

.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(11,16,32,.85);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  max-width: 1200px; margin: 0 auto; padding: 14px 20px;
  display: flex; align-items: center; gap: 24px; flex-wrap: wrap;
}
.brand {
  font-weight: 800; font-size: 1.15rem;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.nav a.navlink {
  color: var(--ink-dim); padding: 6px 10px; border-radius: 8px;
  font-weight: 500;
}
.nav a.navlink:hover, .nav a.navlink.active {
  background: var(--card); color: var(--ink); text-decoration: none;
}
.nav .spacer { flex: 1; }
.nav .who { color: var(--ink-dim); font-size: .9rem; }

.wrap { max-width: 1200px; margin: 0 auto; padding: 28px 20px; }

.hero {
  padding: 60px 20px; text-align: center;
}
.hero h1 {
  font-size: clamp(2rem, 5vw, 3.4rem); margin-bottom: 12px;
  background: linear-gradient(90deg, #fff, var(--accent) 60%, var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p.tag { color: var(--ink-dim); max-width: 640px; margin: 0 auto 28px; font-size: 1.1rem; }

.grid {
  display: grid; gap: 18px;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}
.card {
  background: linear-gradient(180deg, var(--card), var(--bg-soft));
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  transition: transform .15s, border-color .15s;
}
.card:hover { transform: translateY(-2px); border-color: var(--accent); }
.card h3 { margin-top: 0; }
.card .meta { color: var(--ink-dim); font-size: .85rem; }
.card .cta { display: inline-block; margin-top: 12px; color: var(--accent); font-weight: 600; }

.btn {
  display: inline-block; cursor: pointer;
  padding: 10px 18px; border-radius: 10px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: #0b1020; font-weight: 700; border: 0;
  text-decoration: none;
}
.btn:hover { filter: brightness(1.1); text-decoration: none; }
.btn.ghost { background: transparent; border: 1px solid var(--line); color: var(--ink); }

.input, .select, textarea {
  background: var(--bg-soft); color: var(--ink);
  border: 1px solid var(--line); border-radius: 10px;
  padding: 10px 12px; font-size: 1rem; width: 100%;
}
.input:focus, .select:focus, textarea:focus { outline: 2px solid var(--accent); border-color: var(--accent); }

.row { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; }
.muted { color: var(--ink-dim); }
.ok { color: var(--good); }
.err { color: var(--bad); }

/* Periodic table */
.pt {
  display: grid;
  grid-template-columns: repeat(18, minmax(46px, 1fr));
  gap: 4px;
  font-size: .75rem;
}
.pt .el {
  aspect-ratio: 1 / 1; border-radius: 6px;
  padding: 4px; cursor: pointer;
  background: var(--bg-soft); border: 1px solid var(--line);
  display: flex; flex-direction: column; justify-content: space-between;
  color: var(--ink); transition: transform .1s, box-shadow .1s;
}
.pt .el:hover { transform: scale(1.08); z-index: 5; box-shadow: 0 6px 20px rgba(0,0,0,.4); }
.pt .el .z { font-size: .65rem; color: var(--ink-dim); }
.pt .el .sym { font-weight: 800; font-size: 1rem; text-align: center; }
.pt .el .mass { font-size: .6rem; text-align: center; color: var(--ink-dim); }
.pt .gap { background: transparent; border: 0; }

/* category colours */
.cat-nm     { background: #1c3a4a; border-color: #2a5a73; }
.cat-ng     { background: #3b2a52; border-color: #5a3f7a; }
.cat-am     { background: #4a2a2a; border-color: #7a3f3f; }
.cat-ae     { background: #4a3a2a; border-color: #7a5a3f; }
.cat-tm     { background: #2a4a3a; border-color: #3f7a5a; }
.cat-mt     { background: #2a3a4a; border-color: #3f5a7a; }
.cat-ml     { background: #3a2a4a; border-color: #5a3f7a; }
.cat-mtl    { background: #4a3a3a; border-color: #7a5a5a; }
.cat-lan    { background: #2a4a4a; border-color: #3f7a7a; }
.cat-act    { background: #4a2a4a; border-color: #7a3f7a; }
.cat-unk    { background: #2a2a3a; border-color: #4a4a5a; }

/* Element detail panel */
.detail {
  position: fixed; right: 20px; bottom: 20px; width: 360px;
  background: var(--card); border: 1px solid var(--accent);
  border-radius: var(--radius); padding: 18px; box-shadow: var(--shadow);
  z-index: 100; display: none;
}
.detail.open { display: block; }
.detail h2 { margin-top: 0; }
.detail .close { float: right; cursor: pointer; color: var(--ink-dim); }
.detail dl { display: grid; grid-template-columns: auto 1fr; gap: 6px 14px; margin: 0; }
.detail dt { color: var(--ink-dim); }
.detail dd { margin: 0; }

/* MCQ */
.q { padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); margin-bottom: 14px; }
.q .stem { font-size: 1.05rem; margin-bottom: 12px; }
.q .opts { display: grid; gap: 8px; }
.q .opt {
  padding: 10px 14px; border-radius: 10px; cursor: pointer;
  background: var(--bg-soft); border: 1px solid var(--line);
}
.q .opt:hover { border-color: var(--accent); }
.q .opt.chosen { border-color: var(--accent); }
.q .opt.correct { border-color: var(--good); background: #1a3a2a; }
.q .opt.wrong { border-color: var(--bad); background: #3a1a1a; }
.q .expl { margin-top: 10px; padding: 10px; background: var(--bg-soft); border-radius: 8px; color: var(--ink-dim); font-size: .92rem; display: none; }
.q.answered .expl { display: block; }

/* Lesson */
.lesson { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 28px; line-height: 1.7; }
.lesson p { margin: 0 0 1em; }
.lesson ul, .lesson ol { padding-left: 24px; }
.lesson table { border-collapse: collapse; margin: 14px 0; }
.lesson th, .lesson td { border: 1px solid var(--line); padding: 6px 10px; }
.lesson .note { background: var(--bg-soft); border-left: 3px solid var(--accent); padding: 10px 14px; border-radius: 6px; margin: 14px 0; }

@media (max-width: 720px) {
  .pt { font-size: .55rem; }
  .pt .el .sym { font-size: .8rem; }
  .detail { left: 10px; right: 10px; width: auto; bottom: 10px; }
}