/* Neural Networks & Deep Learning — shared course styles.
   Linked on every page (style-src 'self' allows it). Pairs with KaTeX CSS
   from cdnjs for math rendering. Mirrors the ML-Foundations dark theme. */

:root {
  --bg: #0f172a;
  --panel: #1e293b;
  --panel-2: #16243d;
  --ink: #f1f5f9;
  --muted: #94a3b8;
  --soft: #cbd5e1;
  --line: #334155;
  --blue: #3b82f6;
  --blue-d: #2563eb;
  --violet: #8b5cf6;
  --indigo: #6366f1;
  --green: #22c55e;
  --green-l: #4ade80;
  --red: #ef4444;
  --amber: #f59e0b;
  --pink: #f472b6;
  --cyan: #22d3ee;
}

* { box-sizing: border-box; }

body {
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  margin: 0;
  padding: 40px 20px;
  line-height: 1.75;
}
.wrap { max-width: 820px; margin: 0 auto; }

h1 {
  font-size: 30px; margin-bottom: 8px;
  background: linear-gradient(135deg, var(--blue), var(--violet));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
h2 { font-size: 21px; margin-top: 36px; margin-bottom: 12px; color: var(--soft); }
h3 { font-size: 17px; color: var(--ink); }
p, li { color: var(--soft); font-size: 15px; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
strong { color: var(--ink); }
em { color: #e2e8f0; }
code.tok {
  background: #0b1324; border: 1px solid var(--line); border-radius: 5px;
  padding: 1px 6px; font-size: 13px; color: #c7d2fe;
}

.meta { color: var(--muted); font-size: 13px; }
.back { display: inline-block; margin-bottom: 22px; color: var(--blue); }
.back:hover { text-decoration: underline; }

.callout {
  background: var(--panel); border-left: 4px solid var(--indigo);
  border-radius: 8px; padding: 16px 20px; margin: 20px 0; color: var(--soft);
}
.anchor {
  background: linear-gradient(135deg, #16243d, #1b1f3a);
  border-left: 4px solid var(--violet);
  border-radius: 8px; padding: 14px 18px; margin: 18px 0; color: var(--soft); font-size: 14.5px;
}
.anchor .tag {
  display: inline-block; font-size: 11px; letter-spacing: .08em; text-transform: uppercase;
  font-weight: 700; color: #c4b5fd; margin-bottom: 4px;
}
.payoff {
  background: #11261c; border-left: 4px solid var(--green);
  border-radius: 8px; padding: 14px 18px; margin: 18px 0; color: #d1fae5; font-size: 14px;
}
.payoff .tag {
  display: inline-block; font-size: 11px; letter-spacing: .08em; text-transform: uppercase;
  font-weight: 700; color: var(--green-l); margin-bottom: 4px;
}

/* Read-only "here's the real code" sidebar — never interactive */
.codecard {
  background: #0b1222; border: 1px solid var(--line); border-left: 4px solid var(--cyan);
  border-radius: 8px; padding: 12px 16px 14px; margin: 18px 0;
}
.codecard .tag {
  display: inline-block; font-size: 11px; letter-spacing: .08em; text-transform: uppercase;
  font-weight: 700; color: #67e8f9; margin-bottom: 8px;
}
.codecard pre {
  margin: 0; overflow-x: auto; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 13px; line-height: 1.6; color: #e2e8f0;
}
.codecard pre .c { color: #64748b; }   /* comment */
.codecard pre .k { color: #c4b5fd; }   /* keyword */
.codecard pre .s { color: #86efac; }   /* string */
.codecard pre .f { color: #93c5fd; }   /* function/name */
.codecard .note { color: var(--muted); font-size: 12.5px; margin: 8px 0 0; }

ul, ol { padding-left: 22px; }
table { width: 100%; border-collapse: collapse; margin: 18px 0; font-size: 14px; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--line); color: var(--soft); }
th { color: var(--muted); font-size: 12px; text-transform: uppercase; letter-spacing: .06em; }

/* ── Math display blocks ── */
.katex { font-size: 1.05em; }
.mathline { margin: 14px 0; text-align: center; overflow-x: auto; overflow-y: hidden; }
.mathline .katex-display { margin: 0; }

/* ── Generic interactive shell ── */
.activity {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: 12px; padding: 18px 20px; margin: 20px 0;
}
.activity-label {
  color: var(--muted); font-size: 12px; text-transform: uppercase; letter-spacing: .07em;
  font-weight: 700; margin-bottom: 12px;
}
.activity-fallback { color: var(--muted); font-size: 14px; margin: 0; }
.activity-done { margin: 10px 0 0; color: var(--muted); font-style: italic; }
.hint { color: var(--muted); font-size: 13px; margin: 10px 0 0; }

/* Step lists (ordered/unordered) used in lesson prose */
.steps { margin: 4px 0 14px; padding-left: 22px; }
.steps li { margin: 0 0 8px; color: var(--soft); line-height: 1.65; }
.steps li:last-child { margin-bottom: 0; }
.steps li strong { color: var(--ink); }

/* Choice buttons (multiple choice / sort) */
.choice-col { display: flex; flex-direction: column; gap: 9px; }
.choice-grid { display: flex; flex-wrap: wrap; gap: 10px; }
.choice-btn {
  background: var(--bg); color: var(--ink); border: 1px solid var(--line);
  border-radius: 8px; padding: 10px 14px; font-size: 14.5px; cursor: pointer;
  transition: border-color .15s, background .15s; font-family: inherit; text-align: left;
}
.choice-btn:hover:not(:disabled) { border-color: var(--blue); }
.choice-btn:disabled { cursor: default; }
.choice-btn.correct { border-color: var(--green); background: #14321f; color: #bbf7d0; }
.choice-btn.wrong { border-color: var(--red); background: #3a1a1a; color: #fecaca; }
.choice-btn.chosen { border-color: var(--blue); background: var(--panel-2); }

.feedback {
  margin-top: 14px; padding: 12px 16px; background: var(--bg);
  border-left: 3px solid var(--blue); border-radius: 6px; color: var(--soft);
  font-size: 14px; line-height: 1.6;
}
.feedback.hidden, .sort-score.hidden { display: none; }
.next-btn {
  display: inline-block; margin-top: 10px; background: var(--blue); color: #fff;
  border: none; border-radius: 6px; padding: 8px 16px; font-size: 14px; cursor: pointer; font-family: inherit;
}
.next-btn:hover { background: var(--blue-d); }

/* Sort / true-false rows */
.sort-row { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; padding: 10px 0; border-bottom: 1px solid #2a3a52; }
.sort-row:last-of-type { border-bottom: none; }
.sort-text { flex: 1 1 220px; color: var(--ink); font-size: 14.5px; }
.sort-buttons { display: flex; gap: 8px; flex-wrap: wrap; }
.sort-btn {
  background: var(--bg); color: var(--soft); border: 1px solid var(--line);
  border-radius: 7px; padding: 7px 12px; font-size: 13px; cursor: pointer; font-family: inherit; white-space: nowrap;
}
.sort-btn:hover:not(:disabled) { border-color: var(--blue); }
.sort-btn:disabled { cursor: default; }
.sort-btn.correct { border-color: var(--green); background: #14321f; color: #bbf7d0; }
.sort-btn.wrong { border-color: var(--red); background: #3a1a1a; color: #fecaca; }
.sort-btn.truth { border-color: var(--green); }
.sort-mark { font-size: 13px; flex-basis: 100%; }
.sort-mark.ok { color: var(--green-l); }
.sort-mark.no { color: #f87171; }
.sort-score {
  margin-top: 14px; padding: 12px 16px; background: var(--bg);
  border-left: 3px solid var(--blue); border-radius: 6px; color: var(--soft); font-size: 14px; line-height: 1.6;
}

/* ── Controls: sliders, number readouts, buttons ── */
.control-row { display: flex; flex-wrap: wrap; gap: 16px 24px; align-items: center; margin: 6px 0 4px; }
.control { display: flex; flex-direction: column; gap: 4px; min-width: 180px; flex: 1 1 200px; }
.control label { font-size: 12.5px; color: var(--muted); display: flex; justify-content: space-between; gap: 10px; }
.control label .val { color: #c7d2fe; font-weight: 700; font-variant-numeric: tabular-nums; }
input[type=range] { width: 100%; accent-color: var(--blue); cursor: pointer; }
.btn {
  background: var(--blue); color: #fff; border: none; border-radius: 8px;
  padding: 9px 16px; font-size: 14px; font-weight: 600; cursor: pointer; font-family: inherit;
}
.btn:hover { background: var(--blue-d); }
.btn:disabled { opacity: .5; cursor: default; }
.btn-ghost { background: transparent; border: 1px solid var(--line); color: var(--soft); }
.btn-ghost:hover { border-color: var(--blue); background: var(--panel-2); }
.btn-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }

/* Readout panels */
.readout { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }
.stat {
  background: var(--bg); border: 1px solid var(--line); border-radius: 9px;
  padding: 10px 14px; min-width: 110px; flex: 1 1 110px;
}
.stat .k { font-size: 11.5px; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; }
.stat .v { font-size: 20px; color: var(--ink); font-weight: 700; font-variant-numeric: tabular-nums; margin-top: 2px; }
.stat .v.hl { color: #93c5fd; }
.stat .v.good { color: var(--green-l); }
.stat .v.bad { color: #f87171; }

/* Canvas / svg holders */
.canvas-hold { display: flex; justify-content: center; flex-wrap: wrap; gap: 14px; margin: 6px 0; }
canvas { max-width: 100%; height: auto; background: #0b1222; border: 1px solid var(--line); border-radius: 10px; touch-action: none; }

/* Toggle chips */
.chip-row { display: flex; flex-wrap: wrap; gap: 9px; margin: 6px 0 4px; }
.chip {
  background: var(--bg); color: var(--soft); border: 1px solid var(--line);
  border-radius: 999px; padding: 7px 14px; font-size: 14px; cursor: pointer; font-family: inherit;
  transition: border-color .15s, background .15s, color .15s; user-select: none;
}
.chip:hover { border-color: var(--blue); }
.chip.on { border-color: var(--violet); background: #281f45; color: #ddd6fe; font-weight: 600; }

/* Bars (loss / probability / variance) */
.belief-bar { height: 26px; background: var(--bg); border: 1px solid var(--line); border-radius: 7px; overflow: hidden; display: flex; }
.belief-bar .fill { background: linear-gradient(90deg, var(--blue), var(--violet)); height: 100%; transition: width .35s ease; }
.belief-bar .fill.spam { background: linear-gradient(90deg, var(--amber), var(--red)); }
.belief-bar .fill.good { background: linear-gradient(90deg, #16a34a, var(--green-l)); }
.belief-row { display: grid; grid-template-columns: 120px 1fr 64px; gap: 10px; align-items: center; margin: 8px 0; }
.belief-row .lbl { font-size: 13px; color: var(--muted); }
.belief-row .pct { font-size: 14px; color: var(--ink); font-weight: 700; text-align: right; font-variant-numeric: tabular-nums; }

/* small note */
.tiny { font-size: 12.5px; color: var(--muted); }
.mono { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.muted { color: var(--muted); font-size: .8em; font-weight: 600; }
.predict-prompt { color: var(--ink); }
.divider { height: 1px; background: var(--line); margin: 26px 0; border: 0; }

/* legend dots for scatter plots */
.legend { display: flex; flex-wrap: wrap; gap: 14px; font-size: 12.5px; color: var(--muted); margin-top: 8px; }
.legend span { display: inline-flex; align-items: center; gap: 6px; }
.legend i { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }

/* weight sliders coloured by sign (used in neuron / network widgets) */
.wlabel { font-variant-numeric: tabular-nums; }
.wpos { color: var(--green-l); }
.wneg { color: #f87171; }

/* lesson nav cards on index */
.lesson-card {
  display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 10px;
  padding: 16px 18px; margin: 12px 0; color: var(--ink); transition: border-color .2s, transform .1s;
}
.lesson-card:hover { border-color: var(--blue); text-decoration: none; transform: translateY(-1px); }
.lesson-card .num { color: var(--muted); font-size: 12px; letter-spacing: .08em; text-transform: uppercase; font-weight: 700; }
.lesson-card h3 { margin: 6px 0 6px; font-size: 17px; }
.lesson-card p { color: var(--muted); font-size: 14px; margin: 0; line-height: 1.55; }
.lesson-card .pillar { font-size: 11px; color: #c4b5fd; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; }
.lesson-card.done { border-color: #14532d; }
.lesson-card .check { color: var(--green-l); font-weight: 700; font-size: 13px; }
.capstone-card { border-color: var(--indigo); background: linear-gradient(135deg, #1e293b, #1e2540); }
.capstone-card:hover { border-color: var(--violet); }
.capstone-card .num { color: #a5b4fc; }
.pillar-head { color: #c4b5fd; font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .08em; margin: 26px 0 2px; }