:root {
  --bg: #f4f7fb;
  --panel: #ffffff;
  --text: #172033;
  --muted: #697386;
  --navy: #173b67;
  --blue: #2f6fed;
  --blue-soft: #eaf1ff;
  --green: #1f8f5f;
  --green-soft: #e6f7ef;
  --red: #c94444;
  --red-soft: #fdecec;
  --border: #dce3ee;
  --shadow: 0 18px 50px rgba(23, 59, 103, .12);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at top left, rgba(47,111,237,.08), transparent 30%),
    var(--bg);
  color: var(--text);
}

button, select, input { font: inherit; }

button { cursor: pointer; }

.app-shell {
  width: min(1000px, calc(100% - 32px));
  margin: 0 auto;
  padding: 32px 0 48px;
}

.site-header {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  align-items: flex-start;
  margin-bottom: 28px;
}

.eyebrow {
  margin: 0 0 6px;
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .14em;
  color: var(--blue);
}

h1, h2, h3, p { margin-top: 0; }

h1 {
  margin-bottom: 6px;
  font-size: clamp(2rem, 5vw, 3.2rem);
  line-height: 1;
  letter-spacing: -.04em;
}

.subtitle {
  color: var(--muted);
  max-width: 680px;
  margin-bottom: 0;
}

.icon-btn {
  width: 46px;
  height: 46px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: white;
  font-size: 1.2rem;
  box-shadow: 0 4px 16px rgba(0,0,0,.05);
}

.screen { display: none; }
.screen.active { display: block; }

.panel, .functions-panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 22px;
  box-shadow: var(--shadow);
}

.setup-panel {
  padding: 30px;
}

.setting-group {
  margin: 24px 0;
}

.setting-group > label,
.dialog-card > label {
  display: block;
  font-weight: 750;
  margin-bottom: 10px;
}

.segmented {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.choice {
  padding: 13px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #fff;
  font-weight: 750;
  color: var(--navy);
}

.choice.active {
  background: var(--blue-soft);
  border-color: var(--blue);
  color: var(--blue);
}

select {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: white;
  color: var(--text);
}

.check-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.check-grid label {
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 12px;
  text-align: center;
  background: #fff;
}

.primary-btn, .secondary-btn, .got-btn, .missed-btn {
  border: 0;
  border-radius: 14px;
  padding: 14px 20px;
  font-weight: 800;
}

.primary-btn {
  width: 100%;
  background: var(--blue);
  color: white;
}

.secondary-btn {
  background: white;
  border: 1px solid var(--border);
  color: var(--navy);
}

.functions-panel {
  margin-top: 18px;
  padding: 22px 26px;
  box-shadow: none;
}

.function-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.function-chips span {
  background: #f3f6fb;
  border: 1px solid var(--border);
  color: #4a5870;
  padding: 7px 10px;
  border-radius: 999px;
  font-size: .9rem;
}

.study-topbar {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: center;
  margin-bottom: 18px;
}

.progress-track {
  width: min(520px, 60vw);
  height: 8px;
  background: #dfe6f0;
  border-radius: 999px;
  overflow: hidden;
  margin-top: 7px;
}

.progress-fill {
  height: 100%;
  width: 0;
  background: var(--blue);
  transition: width .25s ease;
}

.score-mini {
  display: flex;
  gap: 14px;
  font-size: .95rem;
}

.got-mini { color: var(--green); }
.miss-mini { color: var(--red); }

.flashcard {
  min-height: 430px;
  background: white;
  border: 1px solid var(--border);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 30px;
  display: flex;
  flex-direction: column;
}

.card-label {
  font-size: .74rem;
  font-weight: 850;
  letter-spacing: .14em;
  color: var(--muted);
}

.prompt-area {
  flex: 1;
  display: grid;
  place-items: center;
  text-align: center;
}

.function-name {
  font-size: clamp(2.2rem, 7vw, 5rem);
  font-weight: 850;
  letter-spacing: -.04em;
  color: var(--navy);
}

.equation {
  font-family: "Cambria Math", "Times New Roman", serif;
  font-size: clamp(2.6rem, 8vw, 5.2rem);
  line-height: 1.15;
}

.countdown {
  text-align: center;
  color: var(--muted);
  min-height: 22px;
  font-size: .9rem;
}

.graph-wrap {
  width: min(430px, 88vw);
  aspect-ratio: 1 / 1;
}

.graph-wrap svg {
  width: 100%;
  height: 100%;
  display: block;
}

.reveal-controls {
  display: flex;
  justify-content: center;
  margin: 18px 0;
}

.answer-area {
  background: white;
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 24px;
  box-shadow: var(--shadow);
}

.hidden { display: none !important; }

.answer-grid {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 24px;
  align-items: center;
}

.answer-kicker {
  font-size: .74rem;
  font-weight: 850;
  letter-spacing: .14em;
  color: var(--green);
}

.answer-text h2 {
  font-size: 2.2rem;
  margin-bottom: 8px;
}

.answer-equation { font-size: 2.4rem; }

.answer-graph .graph-wrap { width: 100%; }

.response-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 20px;
}

.got-btn {
  background: var(--green);
  color: white;
}

.missed-btn {
  background: var(--red);
  color: white;
}

.results-panel {
  max-width: 700px;
  margin: 0 auto;
  padding: 34px;
  text-align: center;
}

.big-score {
  width: 180px;
  height: 180px;
  margin: 24px auto;
  border-radius: 50%;
  display: grid;
  place-items: center;
  align-content: center;
  background: var(--blue-soft);
  border: 10px solid white;
  box-shadow: 0 0 0 2px var(--blue);
}

.big-score span {
  font-size: 3.1rem;
  font-weight: 900;
  color: var(--blue);
  line-height: 1;
}

.big-score small { color: var(--muted); margin-top: 6px; }

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
  margin: 24px 0;
}

.stats-grid div {
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 16px;
}

.stats-grid strong {
  display: block;
  font-size: 1.8rem;
}

.stats-grid span {
  color: var(--muted);
  font-size: .9rem;
}

.missed-summary {
  text-align: left;
  margin: 24px 0;
}

.missed-summary h3 { margin-bottom: 10px; }

.missed-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.missed-list span {
  background: var(--red-soft);
  color: var(--red);
  border: 1px solid #f3caca;
  padding: 7px 10px;
  border-radius: 999px;
  font-size: .9rem;
}

.results-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

dialog {
  border: none;
  border-radius: 18px;
  padding: 0;
  box-shadow: var(--shadow);
}

dialog::backdrop {
  background: rgba(16, 24, 40, .45);
}

.dialog-card {
  width: min(420px, calc(100vw - 40px));
  padding: 26px;
}

.small-note {
  color: var(--muted);
  font-size: .88rem;
  margin: 10px 0 18px;
}

@media (max-width: 700px) {
  .app-shell { width: min(100% - 20px, 1000px); padding-top: 20px; }
  .site-header { align-items: center; }
  .subtitle { font-size: .93rem; }
  .setup-panel { padding: 22px; }
  .check-grid { grid-template-columns: 1fr; }
  .flashcard { min-height: 360px; padding: 20px; }
  .answer-grid { grid-template-columns: 1fr; }
  .answer-graph { max-width: 260px; margin: 0 auto; }
  .response-buttons, .results-actions { grid-template-columns: 1fr; }
  .study-topbar { align-items: flex-end; }
  .progress-track { width: 55vw; }
}


/* v2 compact, viewport-friendly study layout */
html, body { min-height: 100%; }
body { overflow-x: hidden; }
.app-shell { min-height: 100vh; padding: 14px 0 18px; }
.site-header { margin-bottom: 10px; align-items: center; }
.site-header h1 { font-size: clamp(1.75rem, 4vw, 2.6rem); margin-bottom: 3px; }
.subtitle { font-size: .9rem; }
.study-topbar { margin-bottom: 8px; }
.flashcard {
  min-height: 0;
  height: clamp(255px, 40vh, 350px);
  padding: 16px 20px 10px;
}
.graph-wrap { width: min(300px, 34vh, 76vw); }
.reveal-controls { margin: 8px 0; }
.reveal-controls .secondary-btn { padding: 9px 16px; }
.answer-area { padding: 12px 16px 14px; }
.answer-grid { grid-template-columns: 1fr minmax(145px, 190px); gap: 14px; }
.answer-grid.no-answer-graph { grid-template-columns: 1fr; text-align: center; }
.answer-text h2 { font-size: 1.55rem; margin-bottom: 2px; }
.answer-equation { font-size: 1.8rem; }
.answer-graph .graph-wrap { width: min(165px, 20vh); margin-left: auto; }
.response-buttons { margin-top: 8px; gap: 10px; }
.got-btn, .missed-btn { padding: 10px 16px; }
.countdown { min-height: 16px; font-size: .8rem; }
.equation math, .answer-equation math { font-size: 1em; }

@media (min-width: 701px) and (max-height: 780px) {
  .app-shell { padding-top: 8px; padding-bottom: 8px; }
  .site-header { margin-bottom: 6px; }
  .site-header .subtitle { display: none; }
  .site-header h1 { font-size: 2rem; }
  .flashcard { height: 36vh; min-height: 225px; }
  .graph-wrap { width: min(255px, 31vh); }
  .answer-area { padding: 9px 14px 10px; }
  .answer-grid { grid-template-columns: 1fr 145px; }
  .answer-graph .graph-wrap { width: 138px; }
  .answer-text h2 { font-size: 1.4rem; }
  .answer-equation { font-size: 1.6rem; }
  .response-buttons { margin-top: 6px; }
}

@media (max-width: 700px) {
  .app-shell { width: min(100% - 14px, 1000px); min-height: 100svh; padding: 9px 0 12px; }
  .site-header { margin-bottom: 8px; }
  .site-header .subtitle { display: none; }
  .site-header h1 { font-size: clamp(1.45rem, 7vw, 2rem); }
  .eyebrow { font-size: .65rem; margin-bottom: 3px; }
  .icon-btn { width: 38px; height: 38px; }
  .study-topbar { gap: 8px; margin-bottom: 6px; }
  .progress-track { width: 56vw; }
  .score-mini { gap: 7px; font-size: .82rem; }
  .flashcard { height: min(40svh, 315px); min-height: 235px; padding: 13px 11px 8px; border-radius: 17px; }
  .graph-wrap { width: min(250px, 31svh, 72vw); }
  .function-name { font-size: clamp(2rem, 11vw, 3.25rem); }
  .equation { font-size: clamp(2.25rem, 12vw, 3.7rem); }
  .answer-area { padding: 10px 11px 11px; border-radius: 17px; }
  .answer-grid { grid-template-columns: 1fr 102px; gap: 8px; }
  .answer-text h2 { font-size: 1.15rem; }
  .answer-equation { font-size: 1.35rem; }
  .answer-graph { max-width: none; margin: 0; }
  .answer-graph .graph-wrap { width: 98px; }
  .response-buttons { grid-template-columns: 1fr 1fr; gap: 7px; margin-top: 7px; }
  .got-btn, .missed-btn { padding: 10px 6px; font-size: .9rem; }
}

@media (max-width: 430px) and (max-height: 720px) {
  .eyebrow { display: none; }
  .site-header h1 { font-size: 1.35rem; }
  .flashcard { height: 37svh; min-height: 215px; }
  .graph-wrap { width: min(220px, 28svh, 68vw); }
  .answer-graph .graph-wrap { width: 84px; }
  .answer-text h2 { font-size: 1.05rem; }
  .answer-equation { font-size: 1.2rem; }
}

/* v3: consistently stack revealed answer representations */
.answer-grid,
.answer-grid.no-answer-graph {
  grid-template-columns: 1fr;
  gap: 6px;
  text-align: center;
  justify-items: center;
}

.answer-text {
  text-align: center;
}

.answer-graph {
  margin: 0 auto;
}

.answer-graph .graph-wrap {
  width: min(132px, 16vh);
  margin: 0 auto;
}

@media (min-width: 701px) and (max-height: 780px) {
  .answer-grid,
  .answer-grid.no-answer-graph {
    grid-template-columns: 1fr;
    gap: 4px;
  }

  .answer-graph .graph-wrap {
    width: min(108px, 14vh);
  }
}

@media (max-width: 700px) {
  .answer-grid,
  .answer-grid.no-answer-graph {
    grid-template-columns: 1fr;
    gap: 4px;
  }

  .answer-graph {
    margin: 0 auto;
  }

  .answer-graph .graph-wrap {
    width: min(96px, 13svh);
    margin: 0 auto;
  }
}

@media (max-width: 430px) and (max-height: 720px) {
  .answer-graph .graph-wrap {
    width: min(80px, 11svh);
  }
}