/* ============================================================
   inflection — plotted-curve macro sensei.
   Ink slate base · one confident amber signal · teal data-pair.
   Dark is the primary scheme; a full light scheme mirrors it.
   ============================================================ */

:root {
  /* dark (default) */
  --ink:      #0C1116;   /* page base */
  --panel:    #131A22;   /* card base */
  --panel2:   #18212B;   /* raised */
  --grid:     #202B36;   /* gridlines / hairlines */
  --line:     #2B3947;   /* borders */
  --paper:    #EDF1F5;   /* primary text */
  --mute:     #9DAEBD;   /* secondary text (>= 4.5:1 on --ink) */
  --faint:    #6E7F8E;   /* tertiary text, large only */

  --amber:    #E8B23A;   /* THE signal accent */
  --amber-in: #2A1E05;   /* text on amber */
  --teal:     #3FB0A0;   /* secondary data series (real vs nominal) */
  --rose:     #E8785B;   /* shocks / losses / erosion */

  --amber-dim: rgba(232, 178, 58, 0.14);
  --teal-dim:  rgba(63, 176, 160, 0.15);
  --rose-dim:  rgba(232, 120, 91, 0.15);

  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --radius: 14px;
  --radius-sm: 9px;
  --shadow: 0 22px 50px -30px rgba(0,0,0,0.85);
  --wrap: 1120px;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);

  --plot-stroke: #2B3947;
  --plot-curve: #E8B23A;
  --plot-teal: #3FB0A0;
}

@media (prefers-color-scheme: light) {
  :root {
    --ink:      #F4F1EA;
    --panel:    #FFFFFF;
    --panel2:   #FBF9F3;
    --grid:     #E4DFD3;
    --line:     #D6D0C2;
    --paper:    #1A2229;   /* ~13:1 on paper */
    --mute:     #4E5A64;   /* >= 4.5:1 on light panels */
    --faint:    #6C7883;

    --amber:    #8A5A0F;   /* darkened to AA on white for small text + button */
    --amber-in: #FFFFFF;
    --teal:     #1E7A6E;   /* darkened for AA */
    --rose:     #C1492C;

    --amber-dim: rgba(138, 90, 15, 0.12);
    --teal-dim:  rgba(30, 122, 110, 0.12);
    --rose-dim:  rgba(193, 73, 44, 0.11);

    --shadow: 0 22px 50px -34px rgba(40,32,12,0.35);

    --plot-stroke: #DBD5C7;
    --plot-curve: #A56B12;
    --plot-teal: #1E7A6E;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
  letter-spacing: -0.003em;
  font-variant-numeric: tabular-nums;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(1100px 560px at 85% -10%, var(--amber-dim), transparent 62%),
    radial-gradient(820px 520px at 2% 2%, var(--teal-dim), transparent 55%);
  pointer-events: none;
}

h1, h2, h3, h4 { margin: 0; font-weight: 700; letter-spacing: -0.02em; line-height: 1.1; }
p { margin: 0; }
em { font-style: normal; color: var(--paper); font-weight: 600; }
ul { list-style: none; margin: 0; padding: 0; }

.eyebrow {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--mute);
  font-weight: 600;
}

.skip-link {
  position: absolute; left: 12px; top: -60px;
  background: var(--amber); color: var(--amber-in);
  padding: 10px 16px; border-radius: 10px; font-weight: 700;
  z-index: 60; transition: top 0.18s var(--ease); text-decoration: none;
}
.skip-link:focus { top: 12px; }

a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid var(--amber);
  outline-offset: 2px;
  border-radius: 6px;
}

/* ============================================================
   MASTHEAD + plotted-curve signature
   ============================================================ */
.masthead {
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, color-mix(in srgb, var(--panel) 55%, transparent) 0%, transparent 100%);
}
.masthead__grid {
  position: absolute; inset: 0; z-index: 0;
  mask-image: linear-gradient(180deg, #000 0%, #000 55%, transparent 96%);
  -webkit-mask-image: linear-gradient(180deg, #000 0%, #000 55%, transparent 96%);
  opacity: 0.9;
}
.plot { width: 100%; height: 100%; display: block; }
.plot__grid line { stroke: var(--plot-stroke); stroke-width: 1; vector-effect: non-scaling-stroke; }
.plot__curve {
  fill: none;
  stroke: var(--plot-curve);
  stroke-width: 2.4;
  vector-effect: non-scaling-stroke;
  filter: drop-shadow(0 0 10px color-mix(in srgb, var(--plot-curve) 40%, transparent));
}
.plot__dot { fill: var(--plot-teal); }

.masthead__inner {
  position: relative; z-index: 1;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 20px clamp(20px, 5vw, 44px) 0;
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
}
.brand { display: flex; align-items: center; gap: 11px; }
.brand__mark { width: 30px; height: 30px; }
.brand__name {
  font-size: 1.25rem; font-weight: 800; letter-spacing: -0.04em;
}
.streak {
  display: inline-flex; align-items: baseline; gap: 7px;
  background: var(--amber-dim);
  border: 1px solid color-mix(in srgb, var(--amber) 45%, transparent);
  border-radius: 999px;
  padding: 6px 14px;
}
.streak__flame { color: var(--amber); font-size: 0.7rem; align-self: center; }
.streak__count { font-family: var(--mono); font-weight: 700; font-size: 1.05rem; color: var(--paper); }
.streak__label { font-size: 0.76rem; color: var(--mute); font-weight: 600; }

.masthead__tag {
  position: relative; z-index: 1;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: clamp(26px, 4vw, 44px) clamp(20px, 5vw, 44px) clamp(30px, 4vw, 46px);
}
.masthead__title {
  font-size: clamp(2rem, 5.2vw, 3.35rem);
  margin: 12px 0 0;
  max-width: 20ch;
}
.masthead__accent { color: var(--amber); }
.masthead__lede {
  margin-top: 16px;
  max-width: 62ch;
  color: var(--mute);
  font-size: clamp(0.98rem, 1.3vw, 1.1rem);
}
.masthead__lede em { color: var(--paper); }

/* ============================================================
   BUTTONS
   ============================================================ */
.btn {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: -0.01em;
  border-radius: 11px;
  cursor: pointer;
  border: 1px solid transparent;
  padding: 11px 20px;
  color: var(--paper);
  transition: transform 0.12s var(--ease), background 0.16s var(--ease), border-color 0.16s var(--ease);
}
.btn:active { transform: translateY(1px); }
.btn--primary {
  background: var(--amber);
  color: var(--amber-in);
  box-shadow: 0 12px 30px -14px color-mix(in srgb, var(--amber) 70%, transparent);
}
.btn--primary:hover { filter: brightness(1.06); }
.btn--ghost {
  background: color-mix(in srgb, var(--panel) 60%, transparent);
  border-color: var(--line);
}
.btn--ghost:hover { border-color: var(--mute); background: var(--panel2); }

/* ============================================================
   TODAY
   ============================================================ */
.today__inner {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: clamp(26px, 4vw, 42px) clamp(20px, 5vw, 44px) 0;
}
.today__ribbon {
  display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap;
  margin-bottom: 14px;
}
.today__date {
  font-family: var(--mono);
  font-size: 0.8rem;
  color: var(--amber);
  background: var(--amber-dim);
  border: 1px solid color-mix(in srgb, var(--amber) 40%, transparent);
  padding: 4px 11px; border-radius: 999px;
  font-weight: 600;
}
.today__kicker {
  font-size: 0.74rem; text-transform: uppercase; letter-spacing: 0.18em;
  color: var(--mute); font-weight: 700;
}

/* ============================================================
   CONCEPT CARD
   ============================================================ */
.concept {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.concept--hero { border-color: color-mix(in srgb, var(--amber) 30%, var(--line)); }

.concept__head {
  padding: clamp(20px, 3vw, 30px) clamp(20px, 3vw, 32px) clamp(14px, 2vw, 20px);
  border-bottom: 1px solid var(--grid);
  background: linear-gradient(180deg, var(--panel2), transparent);
}
.concept__tags { display: flex; flex-wrap: wrap; gap: 7px; margin-bottom: 12px; }
.tag {
  font-size: 0.66rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.08em;
  padding: 3px 9px; border-radius: 999px;
  border: 1px solid var(--line);
  color: var(--mute);
  background: color-mix(in srgb, var(--panel2) 70%, transparent);
}
.tag--area {
  color: var(--amber);
  background: var(--amber-dim);
  border-color: color-mix(in srgb, var(--amber) 40%, transparent);
}
.concept__title {
  font-size: clamp(1.5rem, 3vw, 2.1rem);
  letter-spacing: -0.025em;
}
.concept__big {
  margin-top: 12px;
  font-size: clamp(1.02rem, 1.5vw, 1.18rem);
  color: var(--paper);
  max-width: 68ch;
  line-height: 1.5;
}

.concept__body {
  padding: clamp(18px, 3vw, 28px) clamp(20px, 3vw, 32px) clamp(22px, 3vw, 32px);
  display: grid;
  gap: clamp(20px, 3vw, 28px);
}

/* section blocks inside a concept */
.block__label {
  font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.16em;
  color: var(--mute); font-weight: 700; margin-bottom: 9px;
  display: flex; align-items: center; gap: 8px;
}
.block__label::before {
  content: ""; width: 14px; height: 2px; background: var(--amber); border-radius: 2px;
}
.block__text { color: var(--paper); max-width: 70ch; line-height: 1.55; }
.block__text .num { font-family: var(--mono); color: var(--amber); font-weight: 600; }

/* worked example */
.worked {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel2);
  padding: 16px 18px;
}
.worked__row {
  display: flex; justify-content: space-between; gap: 12px;
  font-family: var(--mono); font-size: 0.9rem;
  padding: 5px 0;
}
.worked__row + .worked__row { border-top: 1px dashed var(--grid); }
.worked__row .k { color: var(--mute); }
.worked__row .v { color: var(--paper); font-weight: 600; text-align: right; }
.worked__row--out .v { color: var(--amber); }
.worked__row--out .k { color: var(--paper); font-weight: 700; }

/* formula chip */
.formula {
  font-family: var(--mono);
  font-size: 0.92rem;
  color: var(--teal);
  background: var(--teal-dim);
  border: 1px solid color-mix(in srgb, var(--teal) 35%, transparent);
  border-radius: var(--radius-sm);
  padding: 11px 14px;
  display: inline-block;
  overflow-x: auto; max-width: 100%;
  white-space: nowrap;
}

/* ============================================================
   INTERACTIVE MODEL
   ============================================================ */
.model {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel2);
  padding: clamp(14px, 2vw, 20px);
}
.model__chart {
  width: 100%;
  aspect-ratio: 16 / 8;
  min-height: 180px;
  border-radius: var(--radius-sm);
  background: var(--ink);
  border: 1px solid var(--grid);
  display: block;
}
.model__controls {
  margin-top: 16px;
  display: grid;
  gap: 14px;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
}
.ctrl { display: flex; flex-direction: column; gap: 7px; min-width: 0; }
.ctrl__top { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; }
.ctrl label { font-size: 0.82rem; font-weight: 600; color: var(--mute); }
.ctrl__val {
  font-family: var(--mono); font-size: 0.92rem; font-weight: 700;
  color: var(--amber); font-variant-numeric: tabular-nums;
}
.ctrl input[type=range] {
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 6px; margin: 6px 0;
  background: var(--grid);
  border-radius: 999px;
  cursor: pointer;
}
.ctrl input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 20px; height: 20px; border-radius: 50%;
  background: var(--amber);
  border: 2px solid var(--ink);
  box-shadow: 0 0 0 1px var(--amber);
  cursor: pointer;
}
.ctrl input[type=range]::-moz-range-thumb {
  width: 20px; height: 20px; border-radius: 50%;
  background: var(--amber);
  border: 2px solid var(--ink);
  box-shadow: 0 0 0 1px var(--amber);
  cursor: pointer;
}
.ctrl input[type=range]:hover::-webkit-slider-thumb { filter: brightness(1.1); }

/* readout */
.readout {
  margin-top: 16px;
  display: flex; flex-wrap: wrap; gap: 10px;
}
.stat {
  flex: 1 1 150px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel);
  padding: 11px 14px;
}
.stat__k { font-size: 0.72rem; color: var(--mute); font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; }
.stat__v { font-family: var(--mono); font-size: 1.35rem; font-weight: 700; margin-top: 3px; font-variant-numeric: tabular-nums; }
.stat__v--amber { color: var(--amber); }
.stat__v--teal  { color: var(--teal); }
.stat__v--rose  { color: var(--rose); }
.stat__v--paper { color: var(--paper); }
.stat__note { font-size: 0.74rem; color: var(--mute); margin-top: 3px; }

/* legend (never color-only: always paired with a text label + swatch shape) */
.legend { display: flex; flex-wrap: wrap; gap: 8px 16px; margin-top: 12px; }
.legend__item { display: inline-flex; align-items: center; gap: 7px; font-size: 0.8rem; color: var(--mute); }
.legend__swatch { width: 22px; height: 3px; border-radius: 2px; flex: none; }
.legend__swatch--amber { background: var(--amber); }
.legend__swatch--teal  { background: var(--teal); }
.legend__swatch--rose  { background: var(--rose); border-radius: 2px; height: 0; border-top: 3px dashed var(--rose); }
.legend__swatch--dot { width: 9px; height: 9px; border-radius: 50%; }

/* ============================================================
   CHALLENGE
   ============================================================ */
.challenge {
  border: 1px dashed color-mix(in srgb, var(--teal) 45%, var(--line));
  border-radius: var(--radius-sm);
  background: var(--teal-dim);
  padding: 16px 18px;
}
.challenge__q { color: var(--paper); font-weight: 600; line-height: 1.5; }
.challenge__q .num { font-family: var(--mono); color: var(--teal); }
.challenge__reveal {
  margin-top: 12px;
  background: var(--panel);
  border: 1px solid var(--line);
  color: var(--paper);
  font-weight: 700; font-size: 0.9rem;
  border-radius: 9px;
  padding: 9px 16px; cursor: pointer;
}
.challenge__reveal:hover { border-color: var(--teal); }
.challenge__answer {
  margin-top: 12px; color: var(--paper); line-height: 1.55; max-width: 70ch;
}
.challenge__answer[hidden] { display: none; }
.challenge__answer .num { font-family: var(--mono); color: var(--teal); font-weight: 600; }

/* mark learned */
.concept__foot {
  display: flex; align-items: center; justify-content: space-between;
  gap: 14px; flex-wrap: wrap;
  padding: 16px clamp(20px, 3vw, 32px);
  border-top: 1px solid var(--grid);
  background: var(--panel2);
}
.learn-toggle {
  display: inline-flex; align-items: center; gap: 11px;
  cursor: pointer; font-weight: 600; font-size: 0.92rem;
  color: var(--mute);
}
.learn-toggle input { position: absolute; opacity: 0; width: 1px; height: 1px; }
.learn-toggle__box {
  width: 24px; height: 24px; border-radius: 7px;
  border: 2px solid var(--line);
  background: var(--panel);
  display: grid; place-items: center;
  transition: all 0.15s var(--ease);
  flex: none;
}
.learn-toggle input:hover + .learn-toggle__box { border-color: var(--teal); }
.learn-toggle input:focus-visible + .learn-toggle__box { outline: 3px solid var(--amber); outline-offset: 2px; }
.learn-toggle input:checked + .learn-toggle__box { background: var(--teal); border-color: var(--teal); }
.learn-toggle input:checked + .learn-toggle__box::after {
  content: ""; width: 6px; height: 11px;
  border: solid var(--ink); border-width: 0 2.5px 2.5px 0;
  transform: rotate(45deg) translate(-0.5px, -1px);
}
.learn-toggle input:checked ~ .learn-toggle__label { color: var(--paper); }
.concept__id { font-family: var(--mono); font-size: 0.76rem; color: var(--mute); }

/* deck nav */
.deck {
  display: flex; gap: 10px; flex-wrap: wrap;
  margin-top: 18px;
}
.deck .btn { flex: 1 1 auto; min-width: 120px; }

/* ============================================================
   LIBRARY
   ============================================================ */
.library {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: clamp(40px, 6vw, 72px) clamp(20px, 5vw, 44px) clamp(50px, 7vw, 84px);
}
.library__head { display: flex; align-items: baseline; justify-content: space-between; gap: 14px; flex-wrap: wrap; }
.library__title { font-size: clamp(1.4rem, 3vw, 1.9rem); }
.library__meta { font-size: 0.85rem; color: var(--mute); font-family: var(--mono); }

.filters { display: flex; flex-wrap: wrap; gap: 8px; margin: 20px 0 24px; }
.filter {
  font-size: 0.82rem; font-weight: 600;
  padding: 7px 14px; border-radius: 999px;
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--panel) 60%, transparent);
  color: var(--mute); cursor: pointer;
  transition: all 0.15s var(--ease);
}
.filter:hover { border-color: var(--mute); color: var(--paper); }
.filter[aria-pressed="true"] {
  background: var(--amber);
  color: var(--amber-in);
  border-color: var(--amber);
}
.filter__n { font-family: var(--mono); opacity: 0.8; margin-left: 4px; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(255px, 1fr));
  gap: 14px;
}
.card {
  text-align: left;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  padding: 16px 17px;
  cursor: pointer;
  display: flex; flex-direction: column; gap: 8px;
  transition: transform 0.14s var(--ease), border-color 0.14s var(--ease);
  position: relative;
  color: inherit;
  font: inherit;
}
.card:hover { transform: translateY(-3px); border-color: color-mix(in srgb, var(--amber) 40%, var(--line)); }
.card__area { font-size: 0.66rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--amber); font-weight: 700; }
.card__title { font-size: 1.02rem; font-weight: 700; letter-spacing: -0.015em; line-height: 1.25; }
.card__big { font-size: 0.85rem; color: var(--mute); line-height: 1.45; }
.card.is-learned { border-color: color-mix(in srgb, var(--teal) 45%, var(--line)); }
.card__done {
  position: absolute; top: 12px; right: 12px;
  width: 20px; height: 20px; border-radius: 50%;
  background: var(--teal); display: none; place-items: center;
}
.card.is-learned .card__done { display: grid; }
.card__done::after {
  content: ""; width: 5px; height: 9px;
  border: solid var(--ink); border-width: 0 2px 2px 0;
  transform: rotate(45deg) translate(-0.5px, -1px);
}
.card.is-today { border-color: var(--amber); }
.card__flag {
  position: absolute; top: -9px; left: 14px;
  font-size: 0.62rem; font-weight: 800; text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--amber-in); background: var(--amber);
  padding: 2px 8px; border-radius: 999px;
  display: none;
}
.card.is-today .card__flag { display: block; }

/* ============================================================
   FOOTER
   ============================================================ */
.foot { border-top: 1px solid var(--line); background: var(--panel); }
.foot__inner {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 30px clamp(20px, 5vw, 44px) 44px;
}
.foot__disclaimer { font-size: 0.86rem; color: var(--mute); max-width: 82ch; line-height: 1.6; }
.foot__disclaimer strong { color: var(--paper); }
.foot__disclaimer em { color: var(--amber); font-style: normal; font-weight: 600; }
.foot__meta {
  margin-top: 16px;
  display: flex; flex-wrap: wrap; gap: 8px 10px;
  font-size: 0.78rem; color: var(--mute);
}
.foot__dot { color: var(--line); }

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 620px) {
  .deck .btn { flex: 1 1 45%; }
  .today__ribbon { gap: 8px; }
}

/* ============================================================
   REDUCED MOTION
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; transition-duration: 0.001ms !important; }
}