/* Components added on top of base.css: story steps, widgets, calculator keys, numeric answers, exams. */
:root {
  --w-neutral: #b4b8b2; --w-neutral-ink: #232b27;
  --w-accent: #5dcaa5; --w-accent-ink: #04342c;
  --w-good: #1d9e75; --w-bad: #d85a30; --w-warn: #e0a021; --w-line: #2a78d6; --w-line2: #eb6834;
  --key-bg: #e9ede8; --key-ink: #17221d; --key-2nd: #f3d27a; --key-cpt: #17221d; --key-cpt-ink: #ffffff;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) { --w-neutral: #5d6862; --w-neutral-ink: #f0f3f1; --w-accent: #2f8f6f; --w-accent-ink: #eafff7; --w-line: #5a9cf0; --w-line2: #f08a5c;
    --key-bg: #2a3531; --key-ink: #e6ece8; --key-2nd: #a8842a; --key-cpt: #e6ece8; --key-cpt-ink: #111815; }
}
:root[data-theme="dark"] { --w-neutral: #5d6862; --w-neutral-ink: #f0f3f1; --w-accent: #2f8f6f; --w-accent-ink: #eafff7; --w-line: #5a9cf0; --w-line2: #f08a5c;
  --key-bg: #2a3531; --key-ink: #e6ece8; --key-2nd: #a8842a; --key-cpt: #e6ece8; --key-cpt-ink: #111815; }

/* ---------- story steps ---------- */
.story .lead { font-size: 18.5px; }
.story .term { font-size: 14.5px; color: var(--muted); border-left: 3px solid var(--line); padding-left: 10px; margin-top: 14px; }
.story .term b { color: var(--ink); }
.widget { margin: 16px 0; }
.widget-error { border: 1px dashed var(--bad); color: var(--bad); border-radius: 10px; padding: 10px 14px; font-size: 14px; }
.rail-exam { margin-top: 2px; }

/* ---------- widget primitives (use these inside widgets) ---------- */
.w-row { display: flex; align-items: center; gap: 12px; margin: 8px 0; }
.w-row label { font-size: 14.5px; color: var(--muted); min-width: 150px; }
.w-row input[type="range"] { flex: 1; min-width: 0; accent-color: var(--accent); }
.w-row output, .w-val { font-family: var(--mono); font-size: 14px; min-width: 64px; text-align: right; font-variant-numeric: tabular-nums; }
.w-chips { display: flex; flex-wrap: wrap; gap: 8px; margin: 8px 0; }
.w-chip { all: unset; box-sizing: border-box; cursor: pointer; font-size: 15px; font-weight: 600; padding: 8px 14px; border-radius: 9px; border: 1.5px solid var(--line); background: var(--surface); }
.w-chip:hover { border-color: var(--accent); }
.w-chip:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.w-chip[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); }
.w-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: 12px; }
.w-card { background: var(--bg); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; }
.w-card .ico { font-size: 26px; line-height: 1; }
.w-card h4 { font-family: var(--display); font-size: 17px; font-weight: 700; margin: 8px 0 4px; }
.w-card p { font-size: 15px; color: var(--muted); margin: 0; }
button.w-card { all: unset; box-sizing: border-box; cursor: pointer; background: var(--bg); border: 1.5px solid var(--line); border-radius: 12px; padding: 12px 14px; display: block; }
button.w-card[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); }
button.w-card:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
button.w-card:hover:not([disabled]) { border-color: var(--accent); }
button.w-card[disabled] { cursor: default; }
button.w-card.right { border-color: var(--good); background: var(--good-soft); }
button.w-card.wrong { border-color: var(--bad); background: var(--bad-soft); }
.w-bars { display: grid; gap: 8px; }
.w-bar-row { display: grid; grid-template-columns: 130px minmax(0, 1fr) auto; gap: 10px; align-items: center; }
.w-bar-row .lbl { font-size: 14.5px; color: var(--muted); }
.w-bar-track { display: flex; gap: 2px; height: 28px; }
.w-seg { height: 100%; border-radius: 4px; display: flex; align-items: center; padding: 0 8px; font-size: 12.5px; white-space: nowrap; overflow: hidden; transition: width .35s; min-width: 0; }
.w-seg.neutral { background: var(--w-neutral); color: var(--w-neutral-ink); }
.w-seg.accent { background: var(--w-accent); color: var(--w-accent-ink); }
.w-seg.good { background: var(--w-good); color: #fff; }
.w-seg.bad { background: var(--w-bad); color: #fff; }
.w-seg.warn { background: var(--w-warn); color: #2b1d00; }
.w-diverge { position: relative; height: 28px; border-left: 1.5px dashed var(--muted); margin-left: 50%; }
.w-diverge .w-seg { position: absolute; top: 0; padding: 0; transition: width .4s, left .4s; }
.w-big { display: flex; flex-wrap: wrap; align-items: baseline; gap: 8px; margin: 12px 0 4px; }
.w-big .k { font-size: 15px; color: var(--muted); }
.w-big .v { font-family: var(--display); font-size: 30px; font-weight: 700; font-variant-numeric: tabular-nums; }
.w-formula { font-family: var(--mono); font-size: 14px; color: var(--muted); margin: 0 0 8px; overflow-wrap: anywhere; }
.w-note { font-size: 15px; color: var(--muted); margin: 8px 0 0; }
.w-verdict { font-size: 15px; padding: 9px 13px; border-radius: 9px; margin-top: 8px; }
.w-verdict.ok { background: var(--good-soft); color: var(--good); }
.w-verdict.no { background: var(--bad-soft); color: var(--bad); }
.w-verdict.flat { background: var(--bg); color: var(--muted); }
.w-table { width: 100%; border-collapse: collapse; font-size: 15px; font-variant-numeric: tabular-nums; }
.w-table th, .w-table td { padding: 6px 8px; text-align: right; border-bottom: 1px solid var(--line); }
.w-table th:first-child, .w-table td:first-child { text-align: left; }
.w-table th { font-family: var(--mono); font-size: 12px; font-weight: 500; text-transform: uppercase; letter-spacing: .05em; color: var(--muted); }
.w-table tr.hl td { background: var(--accent-soft); font-weight: 600; }

/* ---------- charts ---------- */
.chart-svg { display: block; width: 100%; height: auto; }
.chart-svg .c-grid { stroke: var(--line); stroke-width: 1; }
.chart-svg .c-axis { stroke: var(--muted); stroke-width: 1; }
.chart-svg .c-tick { font: 12px var(--mono); fill: var(--muted); }
.chart-svg .c-label { font: 13px var(--body); fill: var(--muted); }
.chart-svg .c-text { font: 13px var(--body); fill: var(--ink); }
.chart-svg .c-line { fill: none; stroke: var(--w-line); stroke-width: 2.5; stroke-linejoin: round; stroke-linecap: round; }
.chart-svg .c-line2 { fill: none; stroke: var(--w-line2); stroke-width: 2.5; stroke-linejoin: round; stroke-linecap: round; }
.chart-svg .c-dash { stroke-dasharray: 5 4; }
.chart-svg .c-fill { fill: var(--w-line); opacity: .14; }
.chart-svg .c-dot { fill: var(--w-line); stroke: var(--surface); stroke-width: 2; }
.chart-svg .c-good { fill: var(--w-good); stroke: var(--w-good); }
.chart-svg .c-bad { fill: var(--w-bad); stroke: var(--w-bad); }
.chart-svg .c-mute { fill: var(--muted); stroke: var(--muted); }
.w-legend { display: flex; flex-wrap: wrap; gap: 6px 16px; font-size: 14px; color: var(--muted); margin: 4px 0; }
.w-legend i { display: inline-block; width: 18px; height: 3px; border-radius: 2px; vertical-align: middle; margin-right: 6px; background: var(--w-line); }
.w-legend i.l2 { background: var(--w-line2); }

/* ---------- calculator keystrokes ---------- */
.calcbox { background: var(--bg); border: 1px solid var(--line); border-radius: 12px; padding: 12px 14px; margin: 14px 0; }
.calcbox .tag { font-family: var(--mono); font-size: 11.5px; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); margin-bottom: 8px; }
.calc-step + .calc-step { border-top: 1px dashed var(--line); margin-top: 10px; padding-top: 10px; }
.calc-step .calc-label { font-weight: 600; font-size: 15px; margin-bottom: 4px; }
.calc-step .calc-note { font-size: 14.5px; color: var(--muted); margin: 0 0 6px; max-width: none; }
.keys { display: flex; flex-wrap: wrap; gap: 6px 4px; align-items: center; }
.keys .grp { display: inline-flex; gap: 4px; align-items: center; margin-right: 8px; }
kbd.key { font-family: var(--mono); font-size: 12.5px; font-weight: 500; padding: 4px 8px; border-radius: 6px; background: var(--key-bg); color: var(--key-ink); border: 1px solid var(--line); box-shadow: 0 1.5px 0 var(--line); white-space: nowrap; }
kbd.key.second { background: var(--key-2nd); color: #2b1d00; }
kbd.key.cpt { background: var(--key-cpt); color: var(--key-cpt-ink); }
.keynum { font-family: var(--mono); font-size: 14px; font-variant-numeric: tabular-nums; }
.calc-display { margin-top: 8px; font-family: var(--mono); font-size: 15px; background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 6px 10px; display: inline-block; }
.calc-display b { color: var(--accent); }
.calc-then { font-size: 14.5px; margin: 8px 0 0; max-width: none; }
.hint-btn { all: unset; box-sizing: border-box; cursor: pointer; display: inline-flex; align-items: center; gap: 8px; font-weight: 600; font-size: 15px; padding: 8px 14px; border-radius: 9px; border: 1.5px dashed var(--muted); color: var(--ink); margin: 0 0 14px; }
.hint-btn:hover { background: var(--bg); }
.hint-btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- numeric answers ---------- */
.numeric { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 0 0 8px; }
.numeric .unit { font-family: var(--mono); color: var(--muted); }
.numeric input { font: inherit; font-family: var(--mono); font-size: 18px; width: 200px; max-width: 100%; padding: 10px 12px; border-radius: 9px; border: 1.5px solid var(--line); background: var(--surface); color: var(--ink); }
.numeric input:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.numeric input.right { border-color: var(--good); background: var(--good-soft); }
.numeric input.wrong { border-color: var(--bad); background: var(--bad-soft); }
.field-error { color: var(--bad); font-size: 14.5px; margin: 0 0 12px; min-height: 1em; }
.problems { font-size: 15px; }

/* ---------- exam ---------- */
.exam-bar { display: flex; flex-wrap: wrap; gap: 10px 16px; align-items: center; justify-content: space-between; margin-bottom: 12px; }
.timer { font-family: var(--mono); font-size: 18px; font-variant-numeric: tabular-nums; padding: 4px 10px; border-radius: 8px; background: var(--bg); border: 1px solid var(--line); }
.timer.low { color: var(--bad); border-color: var(--bad); }
.palette { display: flex; flex-wrap: wrap; gap: 6px; margin: 14px 0; }
.palette button { all: unset; box-sizing: border-box; cursor: pointer; width: 34px; height: 34px; border-radius: 8px; display: grid; place-items: center; font-family: var(--mono); font-size: 13px; border: 1.5px solid var(--line); }
.palette button.answered { background: var(--accent-soft); border-color: var(--accent); }
.palette button.here { outline: 2px solid var(--accent); outline-offset: 1px; }
.palette button.ok { background: var(--good-soft); border-color: var(--good); }
.palette button.no { background: var(--bad-soft); border-color: var(--bad); }
.palette button:focus-visible { outline: 2px solid var(--ink); outline-offset: 2px; }
.review-q { border-top: 1px solid var(--line); padding-top: 16px; margin-top: 16px; }

@media (max-width: 820px) {
  .w-row { flex-wrap: wrap; }
  .w-row label { min-width: 100%; }
  .w-bar-row { grid-template-columns: 96px minmax(0, 1fr) auto; }
}
@media (prefers-reduced-motion: reduce) { .w-seg, .w-diverge .w-seg { transition: none; } }

/* ---------- collapsible topic menu ---------- */
.brand { display: flex; align-items: flex-end; gap: 14px; min-width: 0; }
.icon-btn { all: unset; box-sizing: border-box; cursor: pointer; flex: none; width: 42px; height: 42px; border-radius: 10px; display: grid; place-items: center; color: var(--ink); border: 1.5px solid var(--line); background: var(--surface); margin-bottom: 2px; }
.icon-btn:hover { border-color: var(--accent); color: var(--accent); }
.icon-btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.icon-btn .chev { transition: transform .25s; transform-origin: 15px 12px; }
.icon-btn[aria-expanded="false"] .chev { transform: rotate(180deg); }
.layout { transition: grid-template-columns .28s ease, gap .28s ease; }
nav.rail { transition: transform .28s ease, opacity .2s ease, visibility 0s; }
.layout.rail-hidden { grid-template-columns: 0px minmax(0, 1fr); gap: 0; }
.layout.rail-hidden nav.rail { transform: translateX(-110%); opacity: 0; visibility: hidden; transition: transform .28s ease, opacity .2s ease, visibility 0s .28s; overflow: hidden; }
@media (max-width: 820px) {
  .icon-btn { display: none; }                       /* phones use the topic drop-down instead */
  .layout.rail-hidden { grid-template-columns: minmax(0, 1fr); }
}
@media (prefers-reduced-motion: reduce) { .layout, nav.rail, .icon-btn .chev { transition: none; } }
@media (min-width: 821px) {
  .layout.rail-hidden > div { width: 100%; max-width: 860px; justify-self: center; }   /* centre the lesson when the menu is away */
}

/* ---------- top bar: home link, theme chooser, premium ---------- */
header.top { align-items: center; }
.brand { align-items: center; }
.home-link { color: inherit; text-decoration: none; }
.home-link h1 { font-size: clamp(22px, 3vw, 30px); margin: 0; }
.top-tools { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 16px; }
.top-tools .overall { min-width: 200px; flex: 0 1 240px; }
.theme { display: inline-flex; padding: 3px; border-radius: 10px; border: 1.5px solid var(--line); background: var(--surface); }
.theme button { all: unset; box-sizing: border-box; cursor: pointer; font-size: 14px; font-weight: 600; padding: 6px 11px; border-radius: 7px; color: var(--muted); }
.theme button[aria-checked="true"] { background: var(--accent-soft); color: var(--ink); }
.theme button:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.premium-btn { display: inline-flex; align-items: center; gap: 6px; font-weight: 700; font-size: 15px; padding: 9px 14px; border-radius: 10px; text-decoration: none; background: var(--tip-soft); color: var(--tip); border: 1.5px solid var(--tip); }
.premium-btn:hover { filter: brightness(1.05); }
.premium-btn:focus-visible { outline: 2px solid var(--ink); outline-offset: 2px; }
a.btn { text-decoration: none; display: inline-block; }

/* ---------- views without the topic menu: landing, set-up, test, premium ---------- */
body:not([data-view="topic"]) .layout { grid-template-columns: minmax(0, 1fr); gap: 0; }
body:not([data-view="topic"]) nav.rail, body:not([data-view="topic"]) .rail-select,
body:not([data-view="topic"]) #railToggle, body:not([data-view="topic"]) .overall { display: none; }
body:not([data-view="topic"]) .layout > div { width: 100%; max-width: 900px; justify-self: center; }
body[data-view="home"] main.card { background: transparent; border: 0; padding: clamp(8px, 4vw, 40px) 0; }

.home { text-align: center; }
.home .eyebrow { margin: 0 auto 10px; max-width: none; }
.home-title { font-size: clamp(28px, 4.6vw, 46px); line-height: 1.1; max-width: 18ch; margin: 0 auto 28px; }
.home-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(270px, 1fr)); gap: 18px; text-align: left; }
.mode { display: flex; flex-direction: column; gap: 8px; padding: 24px; border-radius: 18px; background: var(--surface); border: 1.5px solid var(--line); color: var(--ink); text-decoration: none; transition: border-color .15s, transform .15s; }
.mode:hover { border-color: var(--accent); transform: translateY(-2px); }
.mode:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
.mode-ico { width: 54px; height: 54px; border-radius: 14px; display: grid; place-items: center; background: var(--accent-soft); color: var(--accent); }
.mode-name { font-family: var(--display); font-weight: 700; font-size: 26px; margin-top: 6px; }
.mode-text { color: var(--muted); }
.mode-meta { font-family: var(--mono); font-size: 12.5px; color: var(--muted); margin-top: 4px; }
.mode-go { margin-top: 10px; align-self: flex-start; font-weight: 700; padding: 11px 18px; border-radius: 9px; background: var(--accent); color: var(--accent-ink); }

.format-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 12px; }
.format { all: unset; box-sizing: border-box; cursor: pointer; display: flex; flex-direction: column; gap: 2px; padding: 16px 18px; border-radius: 12px; border: 1.5px solid var(--line); background: var(--surface); }
.format:hover { border-color: var(--accent); }
.format:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.format[aria-checked="true"] { border-color: var(--accent); background: var(--accent-soft); }
.format-n { font-family: var(--display); font-weight: 700; font-size: 22px; }
.format-t { color: var(--muted); }
.part-list { display: grid; gap: 6px; }
.part-row { display: grid; grid-template-columns: auto minmax(0, 1fr) auto; gap: 12px; align-items: center; padding: 11px 14px; border-radius: 10px; border: 1.5px solid var(--line); cursor: pointer; color: var(--ink); text-decoration: none; }
a.part-row { grid-template-columns: minmax(0, 1fr) auto; }
.part-row:hover { border-color: var(--accent); }
.part-row:has(input:checked) { background: var(--accent-soft); border-color: var(--accent); }
.part-row input { width: 18px; height: 18px; accent-color: var(--accent); }
.part-n { font-family: var(--mono); font-size: 12.5px; color: var(--muted); white-space: nowrap; }
@media (max-width: 820px) { .top-tools { width: 100%; justify-content: space-between; } .part-n { white-space: normal; text-align: right; } }
@media (prefers-reduced-motion: reduce) { .mode { transition: none; } }