/* ============================================================================
   MechanicsMania — design system
   ----------------------------------------------------------------------------
   Everything below is driven by tokens. No component invents its own spacing,
   radius, duration, or colour; it composes them from the scales defined here.
   That constraint is what keeps eleven screens visually consistent.

   Theme: "slate & brass" — the surfaces of a physics classroom (slate board,
   graphite, chalk) with the warm metal of laboratory instruments. A light
   "paper" theme is available via [data-theme="paper"].
   ========================================================================== */

:root {
  /* --- spacing: 4px base, geometric-ish ramp ----------------------------- */
  --space-1: 0.25rem;   /*  4px */
  --space-2: 0.5rem;    /*  8px */
  --space-3: 0.75rem;   /* 12px */
  --space-4: 1rem;      /* 16px */
  --space-5: 1.5rem;    /* 24px */
  --space-6: 2rem;      /* 32px */
  --space-7: 3rem;      /* 48px */
  --space-8: 4rem;      /* 64px */

  /* --- type scale: 1.200 (minor third), rooted at 16px ------------------- */
  --text-xs: 0.694rem;
  --text-sm: 0.833rem;
  --text-base: 1rem;
  --text-md: 1.2rem;
  --text-lg: 1.44rem;
  --text-xl: 1.728rem;
  --text-2xl: 2.074rem;
  --text-3xl: 2.488rem;

  --leading-tight: 1.2;
  --leading-snug: 1.4;
  --leading-normal: 1.6;

  --weight-normal: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-bold: 700;

  --font-sans: "Spectral", Georgia, "Times New Roman", serif;
  --font-mono: "IBM Plex Mono", "SFMono-Regular", Consolas, monospace;
  --font-hand: "Kalam", "Segoe Print", cursive;

  /* --- geometry ---------------------------------------------------------- */
  --radius: 4px;
  --radius-lg: 8px;
  --border: 1px;
  --rule-width: 1px;

  /* --- motion: one easing curve, three durations ------------------------- */
  --ease: cubic-bezier(0.32, 0.72, 0.29, 1);
  --dur-fast: 120ms;
  --dur-base: 220ms;
  --dur-slow: 420ms;

  --measure: 68ch;

  /* --- colour: slate & brass (default) ----------------------------------- */
  --bg: #14181c;
  --bg-raised: #1b2026;
  --bg-sunken: #0f1316;
  --surface: #1b2026;
  --surface-hover: #232931;
  --stage: #10151a;

  --line: #2c343d;
  --line-strong: #3d4751;

  --fg: #e8e6e1;
  --fg-muted: #a4a8ad;
  --fg-subtle: #7b8189;

  --brass: #c9a227;
  --brass-dim: #8a7220;
  --vector-force: #d2504a;
  --vector-velocity: #5b9dd9;
  --vector-accel: #c9a227;
  --vector-energy: #6aa87a;

  --accent: var(--brass);
  --accent-fg: #14181c;

  --focus: #7cb3e8;
  --danger: #d2504a;
  --danger-bg: rgba(210, 80, 74, 0.1);

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.35);

  color-scheme: dark;
}

:root[data-theme="paper"] {
  --bg: #efe9dd;
  --bg-raised: #f7f3ea;
  --bg-sunken: #e4ddcd;
  --surface: #f7f3ea;
  --surface-hover: #ebe4d6;
  --stage: #f2ede2;

  --line: #cdc4b0;
  --line-strong: #a99e86;

  --fg: #22201c;
  --fg-muted: #56514a;
  --fg-subtle: #7c7568;

  --brass: #8a6a1f;
  --brass-dim: #6d541a;
  --vector-force: #9d2f2a;
  --vector-velocity: #24557f;
  --vector-accel: #8a6a1f;
  --vector-energy: #38663f;

  --accent: #24557f;
  --accent-fg: #ffffff;

  --focus: #24557f;
  --danger: #9d2f2a;
  --danger-bg: rgba(157, 47, 42, 0.08);

  --shadow-sm: 0 1px 2px rgba(60, 50, 30, 0.12);
  --shadow-md: 0 4px 12px rgba(60, 50, 30, 0.12);

  color-scheme: light;
}

/* ============================================================================
   base
   ========================================================================== */

*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  font-variant-numeric: tabular-nums;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 {
  margin: 0;
  font-weight: var(--weight-semibold);
  line-height: var(--leading-tight);
  letter-spacing: -0.01em;
}

p { margin: 0; }

button {
  font: inherit;
  color: inherit;
  cursor: pointer;
}

:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
  border-radius: var(--radius);
}
/* Components here set their own display, which outranks the user-agent's
   [hidden] rule -- so `el.hidden = true` left a full-size, focusable, dead
   button on screen. This restores what the attribute is supposed to mean. */
[hidden] { display: none !important; }

:focus:not(:focus-visible) { outline: none; }

/* Headings receive focus on a screen change so assistive technology lands in
   the new content. That is a programmatic move, not a keyboard one, so it
   should not paint a focus ring. */
[tabindex="-1"]:focus { outline: none; }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.hidden { display: none !important; }

/* Honour the OS "reduce motion" setting rather than animating regardless. */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ============================================================================
   app shell
   ========================================================================== */

#app {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Faint slate grid — a chalkboard ruling, not a decorative gradient. */
#bg-field {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-color: var(--bg);
  background-image:
    linear-gradient(to right, var(--line) var(--rule-width), transparent var(--rule-width)),
    linear-gradient(to bottom, var(--line) var(--rule-width), transparent var(--rule-width));
  background-size: 64px 64px;
  opacity: 0.28;
}

.screen {
  display: none;
  flex: 1;
  padding: var(--space-6) var(--space-5);
}
.screen.is-active {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}
#screen-home.is-active,
#screen-reference.is-active {
  justify-content: flex-start;
}

.stack { width: 100%; max-width: 960px; margin: 0 inline; }
.stack--narrow { max-width: 560px; }
.stack--wide { max-width: 1200px; }

/* ============================================================================
   masthead
   ========================================================================== */

.masthead {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  border-bottom: var(--border) solid var(--line);
  background: var(--bg-raised);
}
.masthead[hidden] { display: none; }

.masthead__brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  background: none;
  border: 0;
  padding: var(--space-1);
  border-radius: var(--radius);
}
.masthead__brand .logo { width: 26px; height: 26px; }
.masthead__brand-name {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  letter-spacing: 0.02em;
}

.progress {
  flex: 1;
  height: 2px;
  background: var(--line);
  overflow: hidden;
}
.progress__bar {
  height: 100%;
  width: 0%;
  background: var(--brass);
  transition: width var(--dur-slow) var(--ease);
}

.masthead__actions { display: flex; gap: var(--space-2); }

/* ============================================================================
   buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  letter-spacing: 0.01em;
  border: var(--border) solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--fg);
  transition:
    background var(--dur-fast) var(--ease),
    border-color var(--dur-fast) var(--ease),
    color var(--dur-fast) var(--ease);
}
.btn:hover { background: var(--surface-hover); border-color: var(--fg-subtle); }
.btn:active { background: var(--bg-sunken); }
.btn[disabled] { opacity: 0.5; cursor: not-allowed; }

.btn--primary {
  background: var(--brass);
  border-color: var(--brass);
  color: var(--accent-fg);
  font-weight: var(--weight-semibold);
}
.btn--primary:hover { background: #d8b13a; border-color: #d8b13a; }
:root[data-theme="paper"] .btn--primary { background: var(--accent); border-color: var(--accent); }
:root[data-theme="paper"] .btn--primary:hover { background: #1d456a; border-color: #1d456a; }

.btn--quiet {
  background: transparent;
  border-color: transparent;
  color: var(--fg-muted);
}
.btn--quiet:hover { background: var(--surface-hover); color: var(--fg); border-color: transparent; }

.btn--block { width: 100%; }

.btn--icon {
  padding: 0;
  width: 32px;
  height: 32px;
  flex: 0 0 auto;
}
.btn--icon svg { width: 15px; height: 15px; }

.btn__spinner {
  width: 13px; height: 13px;
  border: 2px solid currentColor;
  border-right-color: transparent;
  border-radius: 50%;
  animation: spin 700ms linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ============================================================================
   home
   ========================================================================== */

.home { max-width: 1080px; width: 100%; margin: 0 auto; }

.home__header {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding-bottom: var(--space-5);
  border-bottom: var(--border) solid var(--line);
  margin-bottom: var(--space-6);
}
.home__logo { width: 60px; height: 60px; flex: 0 0 auto; }
.home__titles { flex: 1; min-width: 0; }
.home__title {
  font-size: var(--text-2xl);
  letter-spacing: -0.02em;
}
.home__tagline {
  color: var(--fg-muted);
  font-size: var(--text-base);
  margin-top: var(--space-1);
}

.figures {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-4);
  margin-bottom: var(--space-6);
}

.figure {
  margin: 0;
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  overflow: hidden;
}
.figure__stage {
  position: relative;
  height: 236px;
  background: var(--stage);
  border-bottom: var(--border) solid var(--line);
}
.figure__stage canvas { display: block; width: 100%; height: 100%; }
.figure__readout {
  position: absolute;
  top: var(--space-3);
  left: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.7;
  white-space: pre;
  color: var(--fg-muted);
  background: color-mix(in srgb, var(--bg-sunken) 82%, transparent);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-3);
  pointer-events: none;
}
.figure figcaption {
  padding: var(--space-3) var(--space-4);
  font-size: var(--text-sm);
  color: var(--fg-muted);
}
.figure figcaption b {
  color: var(--fg);
  font-weight: var(--weight-semibold);
  font-variant-numeric: tabular-nums;
}

.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-5);
  padding-top: var(--space-5);
  border-top: var(--border) solid var(--line);
}
.step__num {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--brass);
  letter-spacing: 0.08em;
}
.step h3 {
  font-size: var(--text-base);
  margin: var(--space-2) 0 var(--space-1);
}
.step p { font-size: var(--text-sm); color: var(--fg-muted); }

.home__cta { margin-top: var(--space-6); display: flex; gap: var(--space-3); }

/* ============================================================================
   page headers
   ========================================================================== */

.page-head { margin-bottom: var(--space-6); }
.page-head__eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--brass);
}
.page-head__title {
  font-size: var(--text-xl);
  margin-top: var(--space-2);
}
.page-head__sub {
  color: var(--fg-muted);
  font-size: var(--text-sm);
  margin-top: var(--space-2);
  max-width: var(--measure);
}

/* ============================================================================
   chapter index
   ========================================================================== */

.chapters {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(272px, 1fr));
  gap: var(--space-3);
}

.chapter {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4);
  text-align: left;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  transition:
    background var(--dur-fast) var(--ease),
    border-color var(--dur-fast) var(--ease);
}
.chapter:hover { background: var(--surface-hover); border-color: var(--line-strong); }
.chapter__head { display: flex; align-items: baseline; gap: var(--space-2); }
.chapter__num {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--brass);
}
.chapter__name {
  font-size: var(--text-base);
  font-weight: var(--weight-semibold);
}
.chapter__topics {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
}
.chapter__topics li {
  font-size: var(--text-sm);
  color: var(--fg-muted);
  padding: var(--space-1) 0;
  border-top: var(--border) solid var(--line);
}
.chapter__topics li:first-child { border-top: 0; }

/* ============================================================================
   option list (sub-type pickers)
   ========================================================================== */

.options { display: flex; flex-direction: column; gap: var(--space-2); }
.option {
  display: flex;
  gap: var(--space-4);
  align-items: flex-start;
  padding: var(--space-4);
  text-align: left;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  transition: background var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.option:hover { background: var(--surface-hover); border-color: var(--line-strong); }
.option__mark {
  flex: 0 0 auto;
  width: 30px; height: 30px;
  display: grid;
  place-items: center;
  color: var(--brass);
  border: var(--border) solid var(--line-strong);
  border-radius: var(--radius);
}
.option__mark svg { width: 17px; height: 17px; }
.option h3 { font-size: var(--text-base); }
.option p { font-size: var(--text-sm); color: var(--fg-muted); margin-top: var(--space-1); }

/* ============================================================================
   panels / prompts
   ========================================================================== */

.panel {
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-6);
}

.note {
  display: flex;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-left: 3px solid var(--brass);
  border-radius: var(--radius);
}
.note__label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--brass);
  flex: 0 0 auto;
  padding-top: 2px;
}
.note p { font-size: var(--text-sm); line-height: var(--leading-normal); white-space: pre-line; }

.aside-note {
  font-family: var(--font-hand);
  font-size: var(--text-md);
  line-height: var(--leading-snug);
  color: var(--fg-muted);
  padding-left: var(--space-4);
  border-left: 2px dashed var(--line-strong);
  margin-top: var(--space-4);
}

.prompt__eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--brass);
}
.prompt__question {
  font-size: var(--text-lg);
  line-height: var(--leading-snug);
  margin: var(--space-3) 0 var(--space-5);
}
.prompt__choices { display: flex; gap: var(--space-3); }
.prompt__field { display: flex; flex-direction: column; gap: var(--space-3); }
.prompt__hint { font-size: var(--text-sm); color: var(--fg-subtle); }
.field-error {
  font-size: var(--text-sm);
  color: var(--danger);
  margin-top: calc(var(--space-1) * -1);
}
.prompt__statement {
  font-size: var(--text-base);
  color: var(--fg-muted);
  margin-bottom: var(--space-5);
}

.field {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-family: var(--font-mono);
  font-size: var(--text-md);
  background: var(--bg-sunken);
  color: var(--fg);
  border: var(--border) solid var(--line-strong);
  border-radius: var(--radius);
  transition: border-color var(--dur-fast) var(--ease);
}
.field::placeholder { color: var(--fg-subtle); font-family: var(--font-sans); }
.field:focus { border-color: var(--focus); }
/* No outline suppression here. A 1px border tint is too weak an indicator on
   its own, and the global :focus-visible rule already draws the right ring. */

/* ============================================================================
   quantity grid (solve-for picker)
   ========================================================================== */

.quantities {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(210px, 1fr));
  gap: var(--space-2);
}
.quantity {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-3) var(--space-4);
  text-align: left;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  transition: background var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.quantity:hover { background: var(--surface-hover); border-color: var(--line-strong); }
.quantity__sym {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--brass);
}
.quantity__name { font-size: var(--text-sm); color: var(--fg-muted); }

/* ============================================================================
   force tally (net force builder)
   ========================================================================== */

.tally { display: flex; flex-direction: column; gap: var(--space-2); margin-bottom: var(--space-4); }
.tally__row { display: flex; gap: var(--space-2); align-items: center; }
.tally__row .field { font-size: var(--text-base); padding: var(--space-2) var(--space-3); }
.tally__sum {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  text-align: right;
  padding: var(--space-2) 0;
  border-top: var(--border) solid var(--line);
}

/* ============================================================================
   results
   ========================================================================== */

.results {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(320px, 0.7fr);
  gap: var(--space-4);
  width: 100%;
  max-width: 1200px;
}
@media (max-width: 900px) {
  .results { grid-template-columns: 1fr; }
}

.viewport {
  position: relative;
  min-height: 420px;
  background: var(--stage);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
/* The tab panel wraps the canvas so the tablist has something to point at
   with aria-controls. It has to fill the stage absolutely: a percentage
   height inside an auto-height parent resolves to auto, which collapses the
   wrapper and leaves the canvas one pixel tall. */
.viewport__panel { position: absolute; inset: 0; }
.viewport canvas { display: block; width: 100%; height: 100%; }
.viewport__label {
  position: absolute;
  left: var(--space-3);
  bottom: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
  background: color-mix(in srgb, var(--bg-sunken) 82%, transparent);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-1) var(--space-3);
}
.viewport__controls {
  position: absolute;
  right: var(--space-3);
  bottom: var(--space-3);
  display: flex;
  gap: var(--space-2);
}

.viewport__tabs {
  position: absolute;
  top: var(--space-3);
  right: var(--space-3);
  display: flex;
  gap: 2px;
  padding: 2px;
  background: color-mix(in srgb, var(--bg-sunken) 88%, transparent);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  z-index: 2;
}
.tab {
  padding: var(--space-1) var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  background: transparent;
  border: 0;
  border-radius: 2px;
  color: var(--fg-subtle);
  transition: background var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease);
}
.tab:hover { color: var(--fg); background: var(--surface-hover); }
.tab.is-selected { background: var(--surface-hover); color: var(--brass); }
.tab[hidden] { display: none; }

/* On a touch screen the 32px icon buttons and the compact viewport tabs are
   smaller than a fingertip. Fine pointers keep the tighter geometry the
   layout was drawn around; coarse pointers get real 44px targets. */
@media (pointer: coarse) {
  .btn--icon { width: 44px; height: 44px; }
  .tab { min-height: 44px; padding-inline: var(--space-4); }
  .play-controls .btn { min-height: 44px; }
}

/* --- symbolic-first mode --------------------------------------------- */
.answer__head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  margin-bottom: var(--space-2);
}
.switch {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xs);
  color: var(--fg-subtle);
  cursor: pointer;
  user-select: none;
  flex: 0 0 auto;
}
.switch input {
  appearance: none;
  width: 30px; height: 17px;
  border: var(--border) solid var(--line-strong);
  border-radius: 999px;
  background: var(--bg-sunken);
  position: relative;
  cursor: pointer;
  transition: background var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.switch input::after {
  content: "";
  position: absolute;
  top: 2px; left: 2px;
  width: 11px; height: 11px;
  border-radius: 50%;
  background: var(--fg-subtle);
  transition: transform var(--dur-base) var(--ease), background var(--dur-fast) var(--ease);
}
.switch input:checked { border-color: var(--brass); }
.switch input:checked::after { transform: translateX(13px); background: var(--brass); }

.symbolic {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin: var(--space-2) 0 var(--space-4);
  padding-bottom: var(--space-4);
  border-bottom: var(--border) solid var(--line);
}
.symbolic__expr {
  font-family: var(--font-mono);
  font-size: var(--text-md);
  line-height: var(--leading-snug);
  color: var(--brass);
  background: var(--bg-sunken);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-4);
  overflow-x: auto;
}

.answer {
  display: flex;
  flex-direction: column;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-5);
}
.answer__label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--fg-subtle);
}
.answer__value {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-3xl);
  font-weight: var(--weight-medium);
  letter-spacing: -0.02em;
  color: var(--fg);
  margin: var(--space-2) 0 var(--space-4);
  padding-bottom: var(--space-4);
  border-bottom: var(--border) solid var(--line);
}
.answer__unit {
  font-size: var(--text-md);
  color: var(--brass);
  font-weight: var(--weight-normal);
}
.answer__caveat {
  margin: 0 0 var(--space-4);
  padding-left: var(--space-3);
  border-left: 2px solid var(--brass);
  font-size: var(--text-sm);
  line-height: 1.55;
  color: var(--fg-muted);
}

.answer__equations { display: flex; flex-direction: column; gap: var(--space-3); }
.equation__label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-subtle);
  display: block;
  margin-bottom: var(--space-1);
}
.equation__body {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg);
  background: var(--bg-sunken);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-3);
  overflow-x: auto;
}
.answer__actions {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-top: auto;
  padding-top: var(--space-5);
}

.alert {
  padding: var(--space-4);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  color: var(--fg);
  background: var(--danger-bg);
  border: var(--border) solid var(--danger);
  border-radius: var(--radius);
}
.alert__title {
  display: block;
  font-weight: var(--weight-semibold);
  color: var(--danger);
  margin-bottom: var(--space-1);
}

/* skeleton shown while the solve request is in flight */
.skeleton { display: flex; flex-direction: column; gap: var(--space-3); }
.skeleton__bar {
  height: 12px;
  border-radius: var(--radius);
  background: linear-gradient(90deg, var(--line) 25%, var(--surface-hover) 37%, var(--line) 63%);
  background-size: 400% 100%;
  animation: shimmer 1.4s ease-in-out infinite;
}
.skeleton__bar--lg { height: 34px; }
.skeleton__bar--sm { width: 45%; }
@keyframes shimmer {
  0% { background-position: 100% 0; }
  100% { background-position: 0 0; }
}

/* ============================================================================
   derivation (scroll-revealed)
   ========================================================================== */

.derivation {
  width: 100%;
  max-width: 1200px;
  margin-top: var(--space-4);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-5) var(--space-6);
}
.derivation__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-4);
  padding-bottom: var(--space-3);
  border-bottom: var(--border) solid var(--line);
  margin-bottom: var(--space-5);
}
.derivation__head h2 { font-size: var(--text-md); }
.derivation__head span { font-size: var(--text-sm); color: var(--fg-subtle); }

.derivation__steps {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: step;
}
.step-line {
  display: grid;
  grid-template-columns: 28px 1fr;
  gap: var(--space-4);
  padding: var(--space-3) 0;
  border-top: var(--border) solid var(--line);
  opacity: 0;
  transform: translateY(6px);
  transition: opacity var(--dur-slow) var(--ease), transform var(--dur-slow) var(--ease);
}
.step-line:first-child { border-top: 0; }
.step-line.is-revealed { opacity: 1; transform: none; }
.step-line::before {
  counter-increment: step;
  content: counter(step);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-subtle);
  padding-top: 4px;
}
.step-line__label {
  display: block;
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-subtle);
  margin-bottom: var(--space-1);
}
.step-line__math {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-base);
  line-height: var(--leading-snug);
  color: var(--fg);
  overflow-x: auto;
}
.step-line--result .step-line__math { color: var(--brass); font-weight: var(--weight-medium); }

/* ============================================================================
   worklog
   ========================================================================== */

.worklog {
  width: 100%;
  max-width: 1200px;
  margin-top: var(--space-4);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-4) var(--space-6) var(--space-5);
}
.worklog h2 {
  font-size: var(--text-sm);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-subtle);
  font-family: var(--font-mono);
  font-weight: var(--weight-normal);
  margin-bottom: var(--space-3);
}
.worklog__list { list-style: none; margin: 0; padding: 0; }
.worklog__list li {
  display: flex;
  gap: var(--space-4);
  align-items: baseline;
  padding: var(--space-2) 0;
  border-top: var(--border) solid var(--line);
  font-size: var(--text-sm);
}
.worklog__list li:first-child { border-top: 0; }
.worklog__ctx { color: var(--fg-subtle); flex: 0 0 auto; min-width: 15ch; }
.worklog__q { color: var(--fg-muted); flex: 1; }
.worklog__v { font-family: var(--font-mono); color: var(--brass); }

/* ============================================================================
   playground
   ========================================================================== */

.playground { width: 100%; max-width: 1200px; margin: 0 auto; }
.playground__body {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(300px, 360px);
  gap: var(--space-4);
  align-items: start;
}
@media (max-width: 900px) {
  .playground__body { grid-template-columns: 1fr; }
}
.viewport--play { min-height: 480px; }

.play-panel {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-5);
}

.play-field { display: flex; flex-direction: column; gap: var(--space-2); }
.play-field label {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
  font-size: var(--text-sm);
  color: var(--fg-muted);
}
.play-field__val { font-family: var(--font-mono); color: var(--brass); }
.play-field input[type="range"] {
  appearance: none;
  width: 100%;
  height: 3px;
  border-radius: 999px;
  background: var(--line-strong);
  cursor: pointer;
}
.play-field input[type="range"]::-webkit-slider-thumb {
  appearance: none;
  width: 16px; height: 16px;
  border-radius: 50%;
  background: var(--brass);
  border: 2px solid var(--surface);
  cursor: grab;
}
.play-field input[type="range"]::-moz-range-thumb {
  width: 16px; height: 16px;
  border: 2px solid var(--surface);
  border-radius: 50%;
  background: var(--brass);
  cursor: grab;
}

.btn:disabled { opacity: 0.45; cursor: not-allowed; }

/* ============================================================================
   section index
   ========================================================================== */

.pick-group { margin-bottom: var(--space-6); }
.pick-group__title {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--fg-subtle);
  padding-bottom: var(--space-2);
  margin-bottom: var(--space-4);
  border-bottom: var(--border) solid var(--line);
}
.pick-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-3);
}
.pick-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  text-align: left;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-left: 2px solid var(--brass);
  border-radius: var(--radius);
  transition: border-color var(--dur-fast) var(--ease), transform var(--dur-fast) var(--ease);
}
.pick-card:hover { border-color: var(--line-strong); transform: translateY(-1px); }
.pick-card__num { font-family: var(--font-mono); font-size: var(--text-xs); color: var(--brass); }
.pick-card__name {
  font-weight: var(--weight-semibold);
  font-size: var(--text-md);
  color: var(--fg);
  line-height: var(--leading-tight);
}
.pick-card__blurb { font-size: var(--text-sm); line-height: 1.5; color: var(--fg-muted); }

/* Back controls belong at the head of a page, where a reader looks when they
   want to leave, not stranded under everything else. */
.page-actions--lead {
  margin-top: var(--space-6);
  padding-top: var(--space-4);
  border-top: var(--border) solid var(--line);
}

/* ============================================================================
   founder
   ========================================================================== */

.home__founder {
  margin: var(--space-2) 0 var(--space-3);
  font-size: var(--text-sm);
  color: var(--fg-subtle);
  letter-spacing: 0.01em;
}

/* The name is the only thing on the home page allowed to be ornamental, so it
   earns the small-caps and the brass. Built as a button rather than an anchor
   because it navigates within the app rather than off it. */
.founder-link {
  position: relative;
  padding: 0;
  background: none;
  border: 0;
  font-family: var(--font-sans);
  font-size: inherit;
  font-weight: var(--weight-bold);
  font-variant: small-caps;
  letter-spacing: 0.06em;
  color: var(--brass);
  cursor: pointer;
}
.founder-link::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: -2px;
  height: 1px;
  background: currentColor;
  opacity: 0.35;
  transform: scaleX(0.82);
  transform-origin: left;
  transition: transform var(--dur-base) var(--ease), opacity var(--dur-base) var(--ease);
}
.founder-link:hover::after,
.founder-link:focus-visible::after { transform: scaleX(1); opacity: 0.9; }

.founder { display: flex; flex-direction: column; gap: var(--space-6); max-width: 760px; }

.founder__intro {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  max-width: 64ch;
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--fg-muted);
}

.founder__bullets {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  font-size: var(--text-md);
  line-height: 1.5;
  color: var(--fg);
}
.founder__bullets li {
  position: relative;
  padding-left: var(--space-5);
}
/* A drawn marker rather than a disc, so the list reads as handwritten notes
   rather than a spec sheet. */
.founder__bullets li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.62em;
  width: 12px;
  height: 2px;
  background: var(--brass);
  opacity: 0.8;
}

.founder__section { display: flex; flex-direction: column; gap: var(--space-3); }

.founder__heading {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--fg-subtle);
  padding-bottom: var(--space-2);
  border-bottom: var(--border) solid var(--line);
}

.founder__projects { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: var(--space-3); }

.project {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-4);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-left: 2px solid var(--brass);
  border-radius: var(--radius);
  text-decoration: none;
  transition: border-color var(--dur-fast) var(--ease), transform var(--dur-fast) var(--ease);
}
.project:hover { border-color: var(--line-strong); border-left-color: var(--brass); transform: translateY(-1px); }
.project__name { font-weight: var(--weight-semibold); color: var(--fg); }
.project__host { font-family: var(--font-mono); font-size: var(--text-xs); color: var(--fg-subtle); }

/* Name on the left, socials on the right, dropping under the name when there
   is no room for both on one line. */
.founder__head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-5);
  flex-wrap: wrap;
}
.founder__head .page-head { flex: 1 1 20rem; }

.founder__socials {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  /* Sit at the foot of the header block, so the row reads as sitting UNDER
     the name rather than floating beside the eyebrow above it. */
  align-self: flex-end;
  padding-bottom: 2px;
}
@media (max-width: 620px) { .founder__socials { align-self: flex-start; } }

.project__role {
  margin-top: var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--brass);
}

.social {
  padding: var(--space-2) var(--space-4);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.social:hover { color: var(--fg); border-color: var(--line-strong); }
.social[data-pending="1"] { opacity: 0.5; cursor: not-allowed; }

.founder__note { font-size: var(--text-sm); color: var(--fg-subtle); }

.mg-solution {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--fg-muted);
  white-space: pre-wrap;
  margin: var(--space-3) 0 0;
  padding: var(--space-3);
  background: var(--bg-sunken);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  overflow-x: auto;
}

/* Back belongs at the top. Buried under the content it is only reachable
   after scrolling past everything the reader was trying to leave. */
.page-back {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
}
.btn--back {
  padding-left: var(--space-2);
  padding-right: var(--space-3);
  font-size: var(--text-sm);
}

/* The verdict a reader looks for first. A box, tinted by outcome, so "Direct
   hit" and "Tipped left" are legible at a glance instead of being the opening
   clause of a paragraph. The tint is deliberately light -- it has to read as
   an annotation on the page, not as an alert bar. */
.mg-verdict {
  margin: var(--space-3) 0 0;
  padding: var(--space-2) var(--space-3);
  border: var(--border) solid var(--line-strong);
  border-left-width: 3px;
  border-radius: var(--radius);
  font-family: var(--font-display, var(--font-sans));
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  line-height: 1.45;
  color: var(--fg);
  background: var(--bg-raised);
}
/* One token per outcome, mixed down to a wash so the text stays the thing you
   read. Each rule sets its own background AND border so a viewer whose browser
   lacks color-mix still gets a distinguishable box from the border alone. */
.mg-verdict--hit {
  border-left-color: var(--vector-energy);
  background: color-mix(in srgb, var(--vector-energy) 13%, var(--bg-raised));
}
.mg-verdict--over,
.mg-verdict--under {
  border-left-color: var(--vector-accel);
  background: color-mix(in srgb, var(--vector-accel) 13%, var(--bg-raised));
}
.mg-verdict--miss {
  border-left-color: var(--vector-force);
  background: color-mix(in srgb, var(--vector-force) 13%, var(--bg-raised));
}

/* Naming the specific wrong route is worth more than "incorrect", so it gets
   its own block rather than a sentence appended to the verdict. */
.mg-misconception {
  margin-top: var(--space-3);
  padding: var(--space-3);
  border-left: 3px solid var(--vector-force);
  background: var(--bg-sunken);
  border-radius: var(--radius);
  font-size: var(--text-sm);
  line-height: 1.55;
  color: var(--fg-muted);
}
.mg-misconception strong {
  display: block;
  color: var(--fg);
  margin-bottom: var(--space-1);
}

.aside-note {
  margin: var(--space-2) 0 0;
  font-size: var(--text-sm);
  line-height: 1.5;
  color: var(--fg-subtle);
}

.play-graph {
  margin-top: var(--space-5);
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-4) var(--space-5) var(--space-5);
}
.play-graph__head { margin-bottom: var(--space-4); }
.play-graph__title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  margin: 0 0 var(--space-1);
}
.play-graph__sub {
  margin: 0;
  max-width: 68ch;
  font-size: var(--text-sm);
  line-height: 1.55;
  color: var(--fg-muted);
}
.play-graph__controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
  font-size: var(--text-sm);
  color: var(--fg-muted);
}
.play-graph__controls .field { width: auto; min-width: 10rem; }
.play-graph__controls .btn { margin-left: auto; }
.pg-hints {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  margin-bottom: var(--space-3);
  font-size: var(--text-sm);
  color: var(--fg-subtle);
}
.pg-hints__intro { color: var(--fg-muted); }
.pg-hints__item b { color: var(--brass); font-weight: var(--weight-medium); }

.play-graph__stage { position: relative; height: 340px; }
.play-graph__stage canvas { display: block; width: 100%; height: 100%; }
.play-graph__fit {
  margin: var(--space-3) 0 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  min-height: 1.4em;
}
@media (max-width: 900px) {
  .play-graph__stage { height: 260px; }
  .play-graph__controls .btn { margin-left: 0; }
}

.play-note {
  margin: 0 0 var(--space-3);
  padding-left: var(--space-3);
  border-left: 2px solid var(--brass);
  font-size: var(--text-sm);
  line-height: 1.5;
  color: var(--fg-muted);
}

.play-readout { margin: 0; display: flex; flex-direction: column; }
.play-readout > div {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-2) 0;
  border-top: var(--border) solid var(--line);
}
.play-readout > div:first-child { border-top: 0; }
.play-readout dt { font-size: var(--text-sm); color: var(--fg-muted); }
.play-readout dd { margin: 0; font-family: var(--font-mono); font-size: var(--text-sm); color: var(--fg); }

.play-controls { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-2); }
.play-controls .btn { padding: var(--space-2) var(--space-2); font-size: var(--text-sm); }

.tag {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  padding: 1px var(--space-2);
  border-radius: 999px;
  border: var(--border) solid currentColor;
  opacity: 0.7;
}

/* ============================================================================
   moments of inertia
   ========================================================================== */

.inertia-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: var(--space-3);
}
.inertia-section {
  font-size: var(--text-md);
  margin: var(--space-6) 0 var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: var(--border) solid var(--line);
}
.inertia-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4);
  text-align: left;
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  transition: background var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.inertia-card:hover { background: var(--surface-hover); border-color: var(--line-strong); }
.inertia-card__figure {
  height: 92px;
  background: var(--stage);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
}
.inertia-card__figure canvas { display: block; width: 100%; height: 100%; }
.inertia-card__name { font-size: var(--text-sm); font-weight: var(--weight-semibold); }
.inertia-card__formula {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--brass);
}

.detail-body {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: var(--space-5);
  align-items: start;
}
@media (max-width: 900px) { .detail-body { grid-template-columns: 1fr; } }

.detail-figure {
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  padding: var(--space-4);
}
.detail-canvas-wrap {
  height: 240px;
  background: var(--stage);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
}
.detail-canvas-wrap canvas { display: block; width: 100%; height: 100%; }
.detail-formula {
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  color: var(--brass);
  text-align: center;
  padding: var(--space-4) 0 var(--space-3);
}
.detail-calc { display: flex; flex-direction: column; gap: var(--space-3); }
.detail-calc__row { display: flex; flex-direction: column; gap: var(--space-1); }
.detail-calc__row label { font-size: var(--text-xs); color: var(--fg-muted); }
.detail-calc__out {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
  padding-top: var(--space-3);
  border-top: var(--border) solid var(--line);
  font-family: var(--font-mono);
  font-size: var(--text-md);
}
.detail-calc__out span:first-child { font-size: var(--text-xs); color: var(--fg-subtle); }
.detail-calc__out span:last-child { color: var(--brass); }

.detail-steps h2 { font-size: var(--text-md); margin-bottom: var(--space-4); }
.deriv-list { list-style: none; margin: 0; padding: 0; counter-reset: dstep; }
.deriv-list li {
  display: grid;
  grid-template-columns: 26px 1fr;
  gap: var(--space-3);
  padding: var(--space-3) 0;
  border-top: var(--border) solid var(--line);
}
.deriv-list li:first-child { border-top: 0; }
.deriv-list li::before {
  counter-increment: dstep;
  content: counter(dstep);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-subtle);
  padding-top: 3px;
}
.deriv-list b {
  display: block;
  font-weight: var(--weight-normal);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  margin-bottom: var(--space-1);
}
.deriv-list code {
  font-family: var(--font-mono);
  font-size: var(--text-base);
  color: var(--fg);
  overflow-x: auto;
  display: block;
}
.deriv-list li:last-child code { color: var(--brass); font-weight: var(--weight-medium); }
.detail-remark {
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
  border-left: 3px solid var(--brass);
  background: var(--bg-sunken);
  border-radius: var(--radius);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  line-height: var(--leading-normal);
}

/* ============================================================================
   reference sheet
   ========================================================================== */

.reference { width: 100%; max-width: 1200px; margin: 0 auto; }
.reference__grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-3);
  align-items: start;
}
.card {
  background: var(--surface);
  border: var(--border) solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
.card__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: var(--bg-sunken);
  border-bottom: var(--border) solid var(--line);
}
.card__head h3 { font-size: var(--text-sm); font-weight: var(--weight-semibold); }
.card__weight {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--brass);
  flex: 0 0 auto;
}
.card__rows { list-style: none; margin: 0; padding: 0; }
.card__rows li {
  padding: var(--space-2) var(--space-4);
  border-top: var(--border) solid var(--line);
  font-size: var(--text-sm);
}
.card__rows li:first-child { border-top: 0; }
.card__rows b {
  display: block;
  font-weight: var(--weight-medium);
  color: var(--fg-muted);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 2px;
}
.card__rows code {
  font-family: var(--font-mono);
  color: var(--fg);
  font-size: var(--text-sm);
}
.card__rows li[data-kind="trap"] { background: var(--danger-bg); }
.card__rows li[data-kind="trap"] b { color: var(--danger); }

.source-note {
  margin-top: var(--space-5);
  padding-top: var(--space-4);
  border-top: var(--border) solid var(--line);
  font-size: var(--text-sm);
  color: var(--fg-subtle);
  max-width: var(--measure);
}
.source-note a { color: var(--fg-muted); }

/* ============================================================================
   responsive
   ========================================================================== */

@media (max-width: 640px) {
  :root { --text-3xl: 2.074rem; --text-2xl: 1.728rem; }
  .screen { padding: var(--space-5) var(--space-4); }
  .home__header { flex-direction: column; align-items: flex-start; }
  .prompt__choices { flex-direction: column; }
  .worklog__list li { flex-direction: column; gap: var(--space-1); }
}