/* Shared styles. Fonts: Source Sans 3 (body) and Bitter, a sturdy textbook-style slab
   serif (headings). The Sparx-style theme uses Nunito. If fonts can't load (offline),
   system fonts are used instead. */
@import url("https://fonts.googleapis.com/css2?family=Bitter:wght@500;600;700&family=Source+Sans+3:ital,wght@0,400;0,600;0,700;1,400&family=Nunito:wght@500;700;800&display=swap");

/* ---------- Themes ---------- */

:root {
  --bg: #f4f5f7;
  --surface: #ffffff;
  --surface-2: #eef0f3;
  --text: #16191f;
  --muted: #576070;
  --border: #d6dae1;
  --border-strong: #b9bfca;
  --accent: #3b4fd8;
  --accent-soft: #e4e8fc;
  --accent-ink: #ffffff;
  --good: #15803d;
  --good-soft: #dcfce7;
  --bad: #c2410c;
  --bad-soft: #ffedd5;
  --resultant: #7c3aed;
  --grid: #e4e7ec;
  --art: #7d8796;
  --header-bg: #16191f;
  --header-ink: #ffffff;
  --header-btn: rgba(255, 255, 255, .1);
  --header-btn-border: rgba(255, 255, 255, .18);

  --t-forces: #e11d48;
  --t-electricity: #d97706;
  --t-magnetism: #7c3aed;
  --t-waves: #0284c7;
  --t-energy: #16a34a;
  --t-particles: #0d9488;
  --t-atomic: #db2777;
  --t-space: #4f46e5;
  --t-reference: #475569;

  --f1: #2563eb;
  --f2: #ea580c;
  --f3: #059669;
  --f4: #db2777;
  --f5: #0891b2;
  --f6: #ca8a04;
  --f7: #9333ea;
  --f8: #64748b;

  --radius: 6px;
  --radius-sm: 4px;
  --stroke: 1;
  --font-body: "Source Sans 3", "Segoe UI", -apple-system, Arial, sans-serif;
  --font-head: "Bitter", Georgia, "Times New Roman", serif;
  color-scheme: light;
}

/* Sparx-style: deep navy bar, bright green accent, rounded friendly shapes. */
:root[data-theme="sparx"] {
  --bg: #f1f3f8;
  --surface: #ffffff;
  --surface-2: #eef1f7;
  --text: #1b1f3b;
  --muted: #5a6182;
  --border: #dde1ee;
  --border-strong: #c3c9dc;
  --accent: #17a673;
  --accent-soft: #daf5ea;
  --accent-ink: #ffffff;
  --grid: #e5e8f1;
  --art: #8a91ad;
  --header-bg: #1b1f3b;
  --header-ink: #ffffff;
  --header-btn: rgba(255, 255, 255, .08);
  --header-btn-border: rgba(255, 255, 255, .2);
  --radius: 14px;
  --radius-sm: 10px;
  --radius-pill: 999px;
  --font-body: "Nunito", "Segoe UI", -apple-system, Arial, sans-serif;
  --font-head: "Nunito", "Segoe UI", -apple-system, Arial, sans-serif;
}

/* Lesson: light-blue page, red titles and answers, black text, Calibri throughout.
   Calibri is on Windows; iPads fall back to Carlito/system sans. */
:root[data-theme="lesson"] {
  --bg: #DDEAF6;
  --surface: #ffffff;
  --surface-2: #eef4fb;
  --text: #000000;
  --muted: #333333;
  --border: #b9cde3;
  --border-strong: #8fb0d3;
  --accent: #1d5fa8;
  --accent-soft: #d3e3f5;
  --accent-ink: #ffffff;
  --grid: #dbe6f2;
  --art: #6b7f99;
  --header-bg: #ffffff;
  --header-ink: #000000;
  --header-btn: rgba(0, 0, 0, .04);
  --header-btn-border: rgba(0, 0, 0, .2);
  --title: #FF0000;
  --answer: #FF0000;
  --font-body: Calibri, Carlito, "Segoe UI", -apple-system, Arial, sans-serif;
  --font-head: Calibri, Carlito, "Segoe UI", -apple-system, Arial, sans-serif;
}

:root[data-theme="lesson"] .site-header { border-bottom: 2px solid #FF0000; }
:root[data-theme="lesson"] h1,
:root[data-theme="lesson"] h2,
:root[data-theme="lesson"] h3,
:root[data-theme="lesson"] .panel h2,
:root[data-theme="lesson"] .tool-name,
:root[data-theme="lesson"] .brand-name { color: var(--title); font-weight: 700; }

/* Calibri throughout, including the equation symbols. */
:root[data-theme="lesson"] .eq-main,
:root[data-theme="lesson"] .var-btn .vs,
:root[data-theme="lesson"] .sym-chip b { font-family: var(--font-body); }

/* Written answers / results: red in the Lesson theme, unchanged elsewhere. */
.big-number, .calc-out .ans, .working b, .readouts .v { color: var(--answer, inherit); }

:root[data-theme="sparx"] h1, :root[data-theme="sparx"] h2, :root[data-theme="sparx"] .tool-name { font-weight: 800; }

/* Classroom: bright white panels under a bold teal bar. */
:root[data-theme="classroom"] {
  --bg: #edf1f5;
  --surface: #ffffff;
  --surface-2: #f2f5f8;
  --text: #1d2733;
  --muted: #566475;
  --border: #d3dbe4;
  --border-strong: #b5c1ce;
  --accent: #0b8f84;
  --accent-soft: #d6f2ee;
  --accent-ink: #ffffff;
  --grid: #e3e9ef;
  --art: #8392a3;
  --header-bg: #10a597;
  --header-ink: #ffffff;
  --header-btn: rgba(255, 255, 255, .16);
  --header-btn-border: rgba(255, 255, 255, .35);
  --radius: 10px;
  --radius-sm: 6px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]):not([data-theme="classroom"]):not([data-theme="sparx"]):not([data-theme="lesson"]) {
    --bg: #0e1117;
    --surface: #161a22;
    --surface-2: #1f2430;
    --text: #e8eaef;
    --muted: #a2a9b8;
    --border: #2c3240;
    --border-strong: #3d4556;
    --accent: #8b9bff;
    --accent-soft: #252c50;
    --accent-ink: #0e1117;
    --good: #4ade80;
    --good-soft: #163524;
    --bad: #fb923c;
    --bad-soft: #3d2512;
    --resultant: #c4a5ff;
    --grid: #232937;
    --art: #6f788c;
    --header-bg: #07090d;
    --t-forces: #fb7185;
    --t-electricity: #fbbf24;
    --t-magnetism: #a78bfa;
    --t-waves: #38bdf8;
    --t-energy: #4ade80;
    --t-particles: #2dd4bf;
    --t-atomic: #f472b6;
    --t-space: #818cf8;
    --t-reference: #94a3b8;
    --f1: #60a5fa;
    --f2: #fb923c;
    --f3: #34d399;
    --f4: #f472b6;
    --f5: #22d3ee;
    --f6: #facc15;
    --f7: #c084fc;
    --f8: #94a3b8;
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #0e1117;
  --surface: #161a22;
  --surface-2: #1f2430;
  --text: #e8eaef;
  --muted: #a2a9b8;
  --border: #2c3240;
  --border-strong: #3d4556;
  --accent: #8b9bff;
  --accent-soft: #252c50;
  --accent-ink: #0e1117;
  --good: #4ade80;
  --good-soft: #163524;
  --bad: #fb923c;
  --bad-soft: #3d2512;
  --resultant: #c4a5ff;
  --grid: #232937;
  --art: #6f788c;
  --header-bg: #07090d;
  --t-forces: #fb7185;
  --t-electricity: #fbbf24;
  --t-magnetism: #a78bfa;
  --t-waves: #38bdf8;
  --t-energy: #4ade80;
  --t-particles: #2dd4bf;
  --t-atomic: #f472b6;
  --t-space: #818cf8;
  --t-reference: #94a3b8;
  --f1: #60a5fa;
  --f2: #fb923c;
  --f3: #34d399;
  --f4: #f472b6;
  --f5: #22d3ee;
  --f6: #facc15;
  --f7: #c084fc;
  --f8: #94a3b8;
  color-scheme: dark;
}

/* Projector mode: bigger type, stronger lines, no faint text */
:root[data-projector] {
  font-size: 118%;
  --muted: var(--text);
  --stroke: 1.5;
}

/* ---------- Base ---------- */

* { box-sizing: border-box; }

[hidden] { display: none !important; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 1.02rem;
  line-height: 1.5;
  -webkit-tap-highlight-color: transparent;
}

a { color: var(--accent); }

button, input, select { font: inherit; color: inherit; }

h1, h2, h3, h4 { font-family: var(--font-head); font-weight: 600; line-height: 1.2; margin: 0; }

/* ---------- Header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 16px;
  min-height: 58px;
  background: var(--header-bg);
  color: var(--header-ink);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--header-ink);
  min-width: 0;
}

.brand-mark {
  flex: none;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  background: var(--header-ink);
  color: var(--header-bg);
  display: grid;
  place-items: center;
  font-family: var(--font-head);
  font-weight: 700;
  font-size: .95rem;
}

.brand-mark svg { width: 30px; height: 30px; }

.theme-select { position: relative; padding-right: 30px; }
.theme-select select {
  appearance: none;
  -webkit-appearance: none;
  border: 0;
  background: transparent;
  color: inherit;
  font-weight: 700;
  cursor: pointer;
  padding: 0;
}
.theme-select select option { color: #000; background: #fff; }
.theme-select::after {
  content: "";
  position: absolute;
  right: 12px;
  top: 50%;
  width: 7px;
  height: 7px;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: translateY(-70%) rotate(45deg);
  pointer-events: none;
}

.brand-text { display: flex; flex-direction: column; line-height: 1.1; min-width: 0; }
.brand-name { font-family: var(--font-head); font-weight: 700; font-size: 1.1rem; white-space: nowrap; }
.brand-by { font-size: .75rem; opacity: .75; white-space: nowrap; }

.header-title {
  font-family: var(--font-head);
  font-weight: 500;
  opacity: .8;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  min-width: 0;
  padding-left: 12px;
  border-left: 1px solid var(--header-btn-border);
}

.header-spacer { flex: 1; }

.header-actions { display: flex; gap: 6px; align-items: center; }

.icon-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 40px;
  padding: 6px 12px;
  border: 1px solid var(--header-btn-border);
  border-radius: var(--radius-sm);
  background: var(--header-btn);
  color: var(--header-ink);
  cursor: pointer;
  font-size: .9rem;
  font-weight: 700;
  text-decoration: none;
}

.icon-btn:hover { background: rgba(255, 255, 255, .2); }
.icon-btn[aria-pressed="true"] { background: var(--header-ink); color: var(--header-bg); border-color: var(--header-ink); }
.icon-btn svg { width: 18px; height: 18px; flex: none; }

.theme-switch {
  display: inline-flex;
  border: 1px solid var(--header-btn-border);
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.theme-switch button {
  display: grid;
  place-items: center;
  width: 40px;
  height: 38px;
  border: 0;
  background: var(--header-btn);
  color: var(--header-ink);
  cursor: pointer;
}

.theme-switch button + button { border-left: 1px solid var(--header-btn-border); }
.theme-switch button[aria-pressed="true"] { background: var(--header-ink); color: var(--header-bg); }
.theme-switch svg { width: 18px; height: 18px; }

@media (max-width: 700px) {
  .icon-btn .label, .header-title, .brand-by { display: none; }
  .site-header { gap: 8px; padding: 8px 12px; }
  .brand-name { white-space: normal; font-size: .95rem; line-height: 1.15; }
  .theme-switch button { width: 36px; }
}

@media (max-width: 600px) {
  .site-header.tool .brand-text { display: none; }
}

/* ---------- Page shell ---------- */

.page {
  max-width: 1240px;
  margin: 0 auto;
  padding: 20px 16px 48px;
}

.hero { padding: 16px 0 8px; }
.hero h1 { font-size: clamp(1.6rem, 4vw, 2.3rem); letter-spacing: -.01em; }
.hero p { color: var(--muted); max-width: 62ch; margin: 8px 0 0; }

/* ---------- Filters ---------- */

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin: 20px 0 8px;
}

.search {
  flex: 1 1 220px;
  min-height: 42px;
  padding: 8px 12px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
}

.search:focus { outline: 2px solid var(--accent); outline-offset: 1px; }

.chip-group {
  display: inline-flex;
  flex-wrap: wrap;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--surface);
}

.chip {
  min-height: 40px;
  padding: 4px 14px;
  border: 0;
  background: transparent;
  cursor: pointer;
  font-size: .92rem;
  font-weight: 700;
  color: var(--muted);
}

.chip + .chip { border-left: 1px solid var(--border); }
.chip[aria-pressed="true"] { background: var(--accent); color: var(--accent-ink); }

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 40px;
  padding: 4px 6px;
  font-size: .95rem;
  font-weight: 700;
  cursor: pointer;
  user-select: none;
}

.toggle input { width: 20px; height: 20px; accent-color: var(--accent); }

/* ---------- Topic sections & tool cards ---------- */

.topic { margin-top: 30px; }

.topic-head {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--topic);
}

.topic-head h2 { font-size: 1.25rem; }

.topic-dot { display: none; }

.topic-ref { color: var(--muted); font-size: .88rem; font-weight: 700; }

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 12px;
}

.tool-card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 14px 16px 14px 20px;
  min-height: 150px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--text);
  overflow: hidden;
  transition: border-color .12s ease, background .12s ease;
}

.tool-card::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 5px;
  background: var(--topic);
}

a.tool-card:hover { border-color: var(--topic); }
a.tool-card:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }

.tool-card.soon { background: transparent; border-style: dashed; }
.tool-card.soon::before { opacity: .35; }
.tool-card.soon .tool-name, .tool-card.soon .tool-desc, .tool-card.soon .tool-icon { opacity: .65; }

.tool-top { display: flex; align-items: center; gap: 10px; }

.tool-icon {
  flex: none;
  width: 38px;
  height: 38px;
  border-radius: var(--radius-sm);
  display: grid;
  place-items: center;
  background: color-mix(in srgb, var(--topic) 14%, transparent);
  color: var(--topic);
}

.tool-icon svg { width: 22px; height: 22px; }

.tool-name { font-family: var(--font-head); font-weight: 600; font-size: 1.02rem; line-height: 1.25; }
.tool-desc { color: var(--muted); font-size: .93rem; margin: 0; flex: 1; }

.tags { display: flex; flex-wrap: wrap; gap: 4px; }

.tag {
  font-size: .74rem;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 3px;
  background: var(--surface-2);
  color: var(--muted);
  border: 1px solid var(--border);
  white-space: nowrap;
}

.tag.ht { background: var(--bad-soft); color: var(--bad); border-color: transparent; }
.tag.po { background: var(--accent-soft); color: var(--accent); border-color: transparent; }
.tag.rp { background: var(--good-soft); color: var(--good); border-color: transparent; }
.tag.soon { background: transparent; border-style: dashed; }

.empty { color: var(--muted); padding: 40px 0; text-align: center; }

.footer { color: var(--muted); font-size: .88rem; margin-top: 48px; padding-top: 16px; border-top: 1px solid var(--border); }

/* ---------- Tool pages ---------- */

.tool-page { max-width: 1340px; margin: 0 auto; padding: 18px 16px 40px; }

.tool-intro { margin-bottom: 14px; }
.tool-intro h1 { font-size: clamp(1.45rem, 3vw, 1.9rem); }
.tool-intro p { margin: 4px 0 0; color: var(--muted); max-width: 78ch; }

.spec-line { display: flex; flex-wrap: wrap; gap: 4px; margin-top: 8px; }

.tool-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 340px;
  gap: 16px;
  align-items: start;
}

@media (max-width: 920px) {
  .tool-layout { grid-template-columns: minmax(0, 1fr); }
  /* When stacked, show the side panel straight after the main stage, before extras. */
  .tool-layout > .main-col { display: contents; }
  .tool-layout > aside { order: 1; }
  .tool-layout .after-aside { order: 2; margin-top: 0; }
  .tool-layout > .main-col > .panel + .panel { margin-top: 0; }
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
}

.panel + .panel { margin-top: 12px; }

.panel h2 {
  font-family: var(--font-body);
  font-size: .78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .09em;
  color: var(--muted);
  margin-bottom: 10px;
}

.stage { padding: 0; overflow: hidden; }

.stage svg, .stage canvas { display: block; width: 100%; height: auto; touch-action: none; user-select: none; -webkit-user-select: none; }

.btn-row { display: flex; flex-wrap: wrap; gap: 8px; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 42px;
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--surface);
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  color: var(--text);
}

.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn:disabled { opacity: .5; cursor: default; }

.field { display: flex; flex-direction: column; gap: 4px; margin-bottom: 12px; }
.field label, .field .label { font-size: .88rem; font-weight: 700; color: var(--muted); }

.select, .num {
  min-height: 42px;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--surface);
}

.readout {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 4px 12px;
  font-variant-numeric: tabular-nums;
}

.readout dt { color: var(--muted); font-weight: 700; }
.readout dd { margin: 0; font-weight: 700; text-align: right; }

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-size: .92rem;
}

.badge.good { background: var(--good-soft); color: var(--good); }
.badge.bad { background: var(--bad-soft); color: var(--bad); }
.badge.neutral { background: var(--surface-2); color: var(--muted); }

.note { font-size: .9rem; color: var(--muted); margin: 8px 0 0; }

.big-number { font-family: var(--font-head); font-size: 1.9rem; font-weight: 700; font-variant-numeric: tabular-nums; }

.working { font-size: .94rem; margin: 10px 0 0; padding: 10px 12px; background: var(--surface-2); border-radius: var(--radius-sm); font-variant-numeric: tabular-nums; }
.working p { margin: 2px 0; }

/* Stepper (+/-) used for force sizes */
.stepper {
  display: inline-flex;
  align-items: center;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--surface);
}

.stepper button {
  width: 40px;
  height: 40px;
  border: 0;
  background: var(--surface-2);
  cursor: pointer;
  font-size: 1.2rem;
  font-weight: 700;
}

.stepper button:active { background: var(--accent-soft); }

.stepper output {
  min-width: 56px;
  text-align: center;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

input[type="range"] { width: 100%; accent-color: var(--accent); min-height: 32px; }

/* ---------- Spec coverage panel ---------- */

.spec-panel { margin-top: 20px; }
.spec-panel ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.spec-panel li { display: grid; grid-template-columns: 92px 1fr; gap: 10px; font-size: .94rem; }
.spec-panel .code { font-weight: 700; font-variant-numeric: tabular-nums; color: var(--accent); }

.toast {
  position: fixed;
  left: 50%;
  bottom: 24px;
  transform: translateX(-50%);
  background: var(--text);
  color: var(--bg);
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  font-weight: 700;
  opacity: 0;
  pointer-events: none;
  transition: opacity .2s ease;
  z-index: 50;
}

.toast.show { opacity: 1; }

/* Buttons and switches can be pill-shaped in themes that set --radius-pill. */
.icon-btn, .theme-switch, .chip-group, .btn, .stepper, .badge, .search { border-radius: var(--radius-pill, var(--radius-sm)); }
.search { padding-left: 16px; }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}