/* Lab: step-by-step interactive lessons. Builds on ../css/style.css tokens. */
:root {
  --good: #1f9d55;
  --bad: #d6452f;
  --blue: #2f7fd8;
  --paper: #fffdf6;
  --rule: #ece6d4;
  --margin: #e7b9a6;
  --hand: "Caveat", "Segoe Print", "Bradley Hand", cursive;
}
@media (prefers-color-scheme: dark) {
  :root { --good: #3cc46f; --bad: #f0644d; --blue: #5aa2f0; --paper: #14181d; --rule: #222932; --margin: #5a3a32; }
}

.lab-wrap { max-width: 1140px; margin: 0 auto; padding: 0 20px; }
.lab-head { padding: 40px 0 18px; }
.lab-head .eyebrow a { color: inherit; }
.lab-head h1 { font-size: clamp(28px, 4vw, 40px); margin-bottom: 8px; }
.lab-head .lede { font-size: 17px; }

/* layout: the sheet of paper (sketch + working) on the left, the guide on the right.
   On phones: sketch, then the guide, then the working. */
.lesson { display: grid; grid-template-columns: minmax(0, 1.55fr) minmax(0, 1fr); gap: 0 24px;
  grid-template-areas: "sketch panel" "work panel"; align-items: start; }
.sketch { grid-area: sketch; }
.panel { grid-area: panel; position: sticky; top: 16px; }
.working { grid-area: work; }
@media (max-width: 900px) {
  .lesson { grid-template-columns: minmax(0, 1fr); grid-template-areas: "sketch" "panel" "work"; gap: 0; }
  .panel { position: static; margin: 16px 0; }
}

/* the sheet: graph paper behind the sketch, ruled paper behind the working */
.sketch, .working { background-color: var(--paper); border: 1px solid var(--line); }
.sketch { border-radius: 14px 14px 0 0; border-bottom: 0; padding: 14px 14px 8px;
  background-image: linear-gradient(var(--rule) 1px, transparent 1px), linear-gradient(90deg, var(--rule) 1px, transparent 1px);
  background-size: 22px 22px; background-position: -1px -1px; }
.sketch canvas { width: 100%; height: 380px; display: block; touch-action: pan-y; }
@media (max-width: 560px) { .sketch canvas { height: 270px; } }
@media (max-width: 900px) { .sketch { border-radius: 14px; border-bottom: 1px solid var(--line); } .working { border-radius: 14px; } }
.board-foot { display: flex; justify-content: space-between; align-items: center; gap: 10px; flex-wrap: wrap; margin-top: 8px; font: 12px var(--mono); color: var(--muted); }
.legend { display: flex; gap: 14px; flex-wrap: wrap; }
.legend span::before { content: ""; display: inline-block; width: 14px; height: 3px; border-radius: 2px; margin-right: 6px; vertical-align: middle; background: var(--sw, var(--ink)); }
.verdict { font: 600 13px var(--mono); }
.verdict.good { color: var(--good); }
.verdict.bad { color: var(--bad); }

.working { border-radius: 0 0 14px 14px; padding: 18px 18px 26px 0; min-height: 120px;
  background-image: linear-gradient(90deg, transparent 47px, var(--margin) 47px, var(--margin) 48px, transparent 48px),
                    repeating-linear-gradient(transparent 0 43px, var(--rule) 43px 44px);
  background-position: 0 0, 0 12px; }
.working:empty::before { content: "Working appears here, line by line."; display: block; padding-left: 60px; font: 20px var(--hand); color: var(--muted); }
.wline { display: grid; grid-template-columns: 48px minmax(0, 1fr); align-items: center; min-height: 44px; }
/* maths and its margin note share a row; a long equation pushes the note underneath */
.wbody { display: flex; flex-wrap: wrap; align-items: center; gap: 0 14px; min-width: 0; padding: 4px 0; }
.wbody .wmath { flex: 0 1 auto; max-width: 100%; }
.wbody .wnote { flex: 1 0 190px; padding-left: 12px; }
.wnum { font: 600 13px var(--mono); color: var(--muted); text-align: center; align-self: start; padding-top: 12px; }
.wmath { padding-left: 12px; overflow-x: auto; overflow-y: hidden; font-size: 17px; color: var(--ink); opacity: 0.55; transition: opacity .3s; }
.wmath .katex { white-space: nowrap; }
.wnote { font: 21px/1.1 var(--hand); color: var(--accent-2); opacity: 0.55; transition: opacity .3s; }
.wline.now .wmath, .wline.now .wnote { opacity: 1; }
.wline.now .wnum { color: var(--accent); }
@media (max-width: 700px) {
  .wline { grid-template-columns: 34px minmax(0, 1fr); min-height: 0; padding: 2px 0; }
  .wmath { font-size: 15px; padding: 2px 0 2px 12px; }
  .wbody .wnote { flex-basis: 100%; font-size: 19px; }
  .working { background-image: linear-gradient(90deg, transparent 33px, var(--margin) 33px, var(--margin) 34px, transparent 34px); }
}
/* writing in: each new line is revealed left to right, then its margin note */
.wline.writing .wmath { animation: write 0.85s ease-out both; animation-delay: var(--d); }
.wline.writing .wnote { animation: fadein 0.5s ease-out both; animation-delay: calc(var(--d) + 0.7s); }
@keyframes write { from { clip-path: inset(0 100% 0 0); } to { clip-path: inset(0 0 0 0); } }
@keyframes fadein { from { opacity: 0; transform: translateX(-6px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .wline.writing .wmath, .wline.writing .wnote { animation: none; } }

.panel { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 20px 22px; display: flex; flex-direction: column; gap: 14px; min-width: 0; }
.progress { display: flex; gap: 6px; flex-wrap: wrap; }
.progress button { width: 26px; height: 6px; border-radius: 3px; border: 0; padding: 0; background: var(--line); cursor: pointer; }
.progress button.done { background: color-mix(in srgb, var(--accent) 45%, var(--line)); }
.progress button.on { background: var(--accent); }
.step-count { font: 12px var(--mono); color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em; margin: 0; }
.panel h2 { margin: 0; font-size: 24px; }
.panel .text p { margin: 0 0 10px; }
.panel .text p:last-child { margin-bottom: 0; }
.panel .tex { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.panel .tex .katex-display { margin: 0.4em 0; }
.try { border-top: 1px dashed var(--line); padding-top: 12px; display: flex; flex-direction: column; gap: 12px; }
.try-label { font: 12px var(--mono); color: var(--accent-2); text-transform: uppercase; letter-spacing: 0.1em; margin: 0; }
.ctl { display: flex; flex-direction: column; gap: 4px; font-size: 14px; }
.ctl .row { display: flex; justify-content: space-between; gap: 10px; }
.ctl .val { font-family: var(--mono); color: var(--accent); }
.ctl input[type=range] { width: 100%; accent-color: var(--accent); }
.btns { display: flex; gap: 8px; flex-wrap: wrap; }
.nav-row { display: flex; justify-content: space-between; gap: 10px; margin-top: 4px; }
.nav-row .btn { cursor: pointer; font: inherit; font-size: 15px; }
.nav-row .btn[disabled] { opacity: 0.4; cursor: default; }
.kbd-hint { font: 12px var(--mono); color: var(--muted); margin: 0; }

.lesson-nav { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; margin: 40px 0 0; font-size: 15px; }
.lab-cards .card .num { font: 600 13px var(--mono); color: var(--accent); }
.lab-cards .card .steps { font: 12px var(--mono); color: var(--muted); margin-top: auto; padding-top: 10px; }

/* calculator exercises */
.problem { background: color-mix(in srgb, var(--accent) 7%, transparent); border-left: 3px solid var(--accent); padding: 10px 14px; border-radius: 0 8px 8px 0; }
.problem p { margin: 0 0 6px; }
.problem p:last-child { margin: 0; }
.ans { display: flex; flex-direction: column; gap: 4px; font-size: 14px; }
.ans-in { display: flex; align-items: center; gap: 8px; }
.ans input { font: 15px var(--mono); width: 9.5em; max-width: 60%; padding: 6px 9px; border-radius: 6px; border: 1px solid var(--line); background: var(--bg); color: var(--ink); }
.ans input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
.ans .unit { font: 13px var(--mono); color: var(--muted); }
.ans .mark { font: 600 16px var(--mono); }
.mark.good { color: var(--good); }
.mark.bad { color: var(--bad); }
.btn-small.check { background: var(--accent); color: #fff; border-color: var(--accent); }