:root {
  color-scheme: light;
  --ink: #14213d;
  --ink-soft: #59677b;
  --paper: #f4f7fb;
  --surface: #ffffff;
  --line: #dce3ed;
  --navy: #14213d;
  --navy-2: #29466f;
  --accent: #ed6846;
  --accent-soft: #fff0eb;
  --success: #168261;
  --danger: #c94444;
  --warning: #b66a05;
  --shadow: 0 16px 44px rgba(20, 33, 61, .10);
  --shadow-soft: 0 7px 22px rgba(20, 33, 61, .07);
  --antiquity: #d46a25;
  --middle: #3d6ec9;
  --modern: #a34570;
  --contemporary: #13877d;
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --ink: #f5f7fb;
  --ink-soft: #aeb9c9;
  --paper: #0e1727;
  --surface: #172338;
  --line: #2d3a50;
  --navy: #f5f7fb;
  --navy-2: #b7c9e3;
  --accent: #ff8a68;
  --accent-soft: #42281f;
  --success: #78c9aa;
  --danger: #f08d8d;
  --warning: #e2b262;
  --shadow: 0 18px 42px rgba(0, 0, 0, .22);
  --antiquity: #d98a54;
  --middle: #79a9d2;
  --modern: #d0829b;
  --contemporary: #6dbcb5;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-width: 320px;
  background: var(--paper);
  color: var(--ink);
  font-family: Arial, Helvetica, sans-serif;
  font-size: 17px;
  line-height: 1.58;
  -webkit-font-smoothing: antialiased;
}

button, input, select { font: inherit; }
button, label { -webkit-tap-highlight-color: transparent; }
button { color: inherit; }

.skip-link {
  position: fixed;
  top: .5rem;
  left: .5rem;
  z-index: 100;
  padding: .75rem 1rem;
  background: var(--surface);
  color: var(--ink);
  border-radius: .5rem;
  transform: translateY(-160%);
}
.skip-link:focus { transform: none; }

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

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4.4rem;
  padding: 0 1rem;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  border-bottom: 1px solid color-mix(in srgb, var(--line) 72%, transparent);
  backdrop-filter: blur(16px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .65rem;
  padding: .35rem;
  background: none;
  border: 0;
  font-weight: 800;
  letter-spacing: -.02em;
  cursor: pointer;
}

.brand-mark {
  display: grid;
  width: 2rem;
  height: 2rem;
  place-items: center;
  border-radius: .7rem;
  background: var(--accent);
  color: #fff;
  font-family: inherit;
  font-weight: 900;
}
.brand-mark svg, .action-icon, .bottom-nav svg { fill: none; stroke: currentColor; stroke-width: 1.9; stroke-linecap: round; stroke-linejoin: round; }
.brand-mark svg { width: 1.25rem; height: 1.25rem; }
.action-icon { width: 1.2rem; height: 1.2rem; flex: 0 0 auto; }

.icon-button {
  display: grid;
  width: 2.75rem;
  height: 2.75rem;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--surface);
  cursor: pointer;
}

.secure-warning { width: min(calc(100% - 2rem), 72rem); margin: .75rem auto 0; padding: .7rem .9rem; border: 1px solid color-mix(in srgb, var(--warning) 35%, var(--line)); border-radius: .8rem; background: color-mix(in srgb, var(--warning) 9%, var(--surface)); color: var(--ink); font-size: .82rem; font-weight: 650; }

main {
  width: min(100%, 72rem);
  margin: 0 auto;
  padding: 1rem 1rem calc(6.5rem + var(--safe-bottom));
}

.view { display: none; animation: view-in .22s ease both; }
.view.is-active { display: block; }
@keyframes view-in { from { opacity: 0; transform: translateY(5px); } }

h1, h2, h3, p { margin-top: 0; }
h1, h2, h3 { font-family: Arial, Helvetica, sans-serif; line-height: 1.18; letter-spacing: -.015em; }
h1 { margin-bottom: .65rem; font-size: clamp(2rem, 8vw, 3.4rem); font-weight: 700; }
h2 { margin-bottom: .4rem; font-size: clamp(1.35rem, 5vw, 2rem); font-weight: 700; }
h3 { font-size: 1.12rem; font-weight: 700; }

.muted { color: var(--ink-soft); }
.eyebrow {
  margin-bottom: .35rem;
  color: var(--accent);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .11em;
  text-transform: uppercase;
}

.home-intro {
  position: relative;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  overflow: hidden;
  margin: .4rem 0 1rem;
  padding: 1.35rem;
  border-radius: 1.5rem;
  background: #14213d;
  color: #fff;
  box-shadow: var(--shadow);
}
.home-intro::after { content: ""; position: absolute; right: -3.6rem; bottom: -5rem; width: 10rem; height: 10rem; border: 1.7rem solid rgba(255, 255, 255, .07); border-radius: 50%; pointer-events: none; }
.home-intro > div:first-child { max-width: 37rem; }
.home-intro .muted { color: #cbd6e7; }
.home-intro .eyebrow { color: #ff9d7f; }

.mastery-ring {
  --progress: 0deg;
  position: relative;
  display: grid;
  flex: 0 0 auto;
  width: 5.5rem;
  height: 5.5rem;
  place-content: center;
  text-align: center;
  border-radius: 50%;
  background: conic-gradient(#ff8a68 var(--progress), rgba(255,255,255,.16) 0);
}
.mastery-ring::before {
  content: "";
  position: absolute;
  inset: .42rem;
  border-radius: inherit;
  background: #14213d;
}
.mastery-ring span, .mastery-ring small { position: relative; }
.mastery-ring span { font-size: 1.1rem; font-weight: 800; }
.mastery-ring small { color: #cbd6e7; font-size: .7rem; }

.primary-action,
.secondary-action,
.small-button,
.text-button {
  border: 0;
  cursor: pointer;
  transition: transform .15s ease, background .15s ease, border-color .15s ease;
}
.primary-action:active, .secondary-action:active, .small-button:active { transform: scale(.985); }
.primary-action:focus-visible, .secondary-action:focus-visible, .small-button:focus-visible,
.icon-button:focus-visible, input:focus-visible, select:focus-visible, summary:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 48%, transparent);
  outline-offset: 2px;
}

.primary-action {
  display: flex;
  min-height: 3.75rem;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: .9rem 1.05rem;
  border-radius: 1.05rem;
  background: var(--ink);
  color: var(--paper);
  font-weight: 800;
}
.review-card {
  width: 100%;
  min-height: 6rem;
  padding: 1.15rem 1.25rem;
  background: var(--accent);
  color: #fff;
  box-shadow: 0 14px 35px color-mix(in srgb, var(--accent) 28%, transparent);
  text-align: left;
}
.review-card small { display: block; margin-bottom: .3rem; color: rgba(255,255,255,.8); }
.review-card strong { font-size: 1.05rem; }
.primary-action:disabled { opacity: .48; cursor: not-allowed; transform: none; }
.round-arrow {
  display: grid;
  width: 2.55rem;
  height: 2.55rem;
  flex: 0 0 auto;
  place-items: center;
  border-radius: 50%;
  background: rgba(255,255,255,.2);
  font-size: 1.25rem;
}

.daily-strip {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .8rem;
  margin-top: .75rem;
  padding: .75rem .85rem;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: var(--surface);
}
.daily-strip p { margin: 0; color: var(--ink-soft); font-size: .78rem; font-weight: 700; }
.daily-strip .small-button { flex: 0 0 auto; min-height: 2.65rem; padding: .45rem .7rem; color: var(--ink); }

.today-panel {
  display: grid;
  gap: 1rem;
  margin-top: 1rem;
  padding: 1.15rem;
  border: 1px solid var(--line);
  border-radius: 1.35rem;
  background: var(--surface);
  box-shadow: var(--shadow-soft);
}
.today-copy h2 { margin-bottom: .25rem; }
.today-copy p:last-child { margin-bottom: 0; }
.today-metrics { display: grid; grid-template-columns: repeat(3, 1fr); gap: .55rem; }
.today-metrics div { display: grid; padding: .75rem .45rem; border-radius: .9rem; background: var(--paper); text-align: center; }
.today-metrics strong { font-size: 1.25rem; line-height: 1.2; }
.today-metrics span { color: var(--ink-soft); font-size: .7rem; }
.daily-goal > div:first-child { display: flex; justify-content: space-between; gap: 1rem; margin-bottom: .4rem; font-size: .82rem; }
.quick-lengths { display: grid; grid-template-columns: repeat(3, 1fr); gap: .55rem; }
.quick-lengths button { min-height: 3.8rem; padding: .55rem .35rem; border: 1px solid var(--line); border-radius: .9rem; background: var(--surface); cursor: pointer; }
.quick-lengths button.is-recommended { border-color: var(--accent); background: var(--accent-soft); }
.quick-lengths strong, .quick-lengths span { display: block; }
.quick-lengths strong { font-size: .86rem; }
.quick-lengths span { color: var(--ink-soft); font-size: .68rem; }
.full-width { width: 100%; }

.section-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 1rem;
  margin: 2rem 0 .9rem;
}
.section-heading.compact { margin: 0 0 1rem; }
.section-heading h2, .section-heading p { margin-bottom: 0; }

.period-grid { display: grid; gap: .75rem; }
.period-card {
  --period-color: var(--accent);
  position: relative;
  overflow: hidden;
  padding: 1.05rem;
  border: 1px solid color-mix(in srgb, var(--period-color) 18%, var(--line));
  border-radius: 1.25rem;
  background: color-mix(in srgb, var(--period-color) 7%, var(--surface));
  box-shadow: var(--shadow-soft);
  transition: transform .18s ease, box-shadow .18s ease;
  width: 100%;
  color: var(--ink);
  font: inherit;
  text-align: left;
  cursor: pointer;
  appearance: none;
}
.period-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.period-card:focus-visible { outline: 3px solid color-mix(in srgb, var(--period-color) 42%, transparent); outline-offset: 3px; }
.period-card-top { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.period-card-title { display: flex; align-items: center; gap: .75rem; }
.period-number { display: grid; width: 2.45rem; height: 2.45rem; flex: 0 0 auto; place-items: center; border-radius: .8rem; background: var(--period-color); color: #fff; font-size: .75rem; font-weight: 900; letter-spacing: .04em; }
.period-card h3 { margin-bottom: .18rem; }
.period-card p { margin-bottom: .75rem; font-size: .85rem; }
.period-card strong { color: var(--period-color); font-size: .85rem; }
.period-card-footer { display: flex; align-items: center; justify-content: space-between; gap: .75rem; margin-top: .75rem; color: var(--ink-soft); font-size: .78rem; font-weight: 750; }
.period-card-footer span:last-child { display: grid; width: 1.8rem; height: 1.8rem; place-items: center; border-radius: 50%; background: var(--period-color); color: #fff; }
.progress-bar { overflow: hidden; height: .42rem; border-radius: 999px; background: var(--line); }
.progress-bar span { display: block; height: 100%; border-radius: inherit; background: var(--period-color, var(--accent)); }

.home-actions { display: grid; gap: .75rem; margin-top: 1.4rem; }
.secondary-action {
  display: flex;
  min-height: 3.75rem;
  align-items: center;
  justify-content: center;
  gap: .6rem;
  padding: .8rem 1rem;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: var(--surface);
  font-weight: 780;
  box-shadow: var(--shadow-soft);
}

.page-heading { margin: .8rem 0 1.8rem; }
.page-heading .muted { max-width: 38rem; }
#view-study .page-heading, #session-form { width: 100%; max-width: 56rem; margin-left: auto; margin-right: auto; }
#view-progress { max-width: 62rem; margin-inline: auto; }

form { display: grid; gap: 1.4rem; }
.session-presets { display: grid; gap: .7rem; }
.session-presets button {
  display: grid;
  gap: .12rem;
  min-height: 5.4rem;
  padding: .9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 1.05rem;
  background: var(--surface);
  color: var(--ink);
  box-shadow: var(--shadow-soft);
  text-align: left;
  cursor: pointer;
}
.session-presets button.is-recommended { border-color: var(--accent); background: var(--accent-soft); }
.session-presets small { color: var(--accent); font-size: .7rem; font-weight: 850; text-transform: uppercase; letter-spacing: .07em; }
.session-presets strong { font-size: 1rem; }
.session-presets span { color: var(--ink-soft); font-size: .78rem; }
.custom-session-options { display: grid; gap: 1.4rem; padding-top: .4rem; }
fieldset { min-width: 0; margin: 0; padding: 0; border: 0; }
legend { width: 100%; margin-bottom: .7rem; font-weight: 800; }

.choice-pills { display: flex; flex-wrap: wrap; gap: .55rem; }
.choice-pills label { cursor: pointer; }
.choice-pills input { position: absolute; opacity: 0; pointer-events: none; }
.choice-pills span, .small-button {
  display: inline-flex;
  min-height: 2.9rem;
  align-items: center;
  justify-content: center;
  padding: .55rem .85rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  font-size: .88rem;
  font-weight: 700;
}
.choice-pills input:checked + span {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--paper);
}
.choice-pills input:focus-visible + span { outline: 3px solid color-mix(in srgb, var(--accent) 48%, transparent); outline-offset: 2px; }

.date-range-fieldset {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 1.2rem;
  background: var(--surface);
  box-shadow: var(--shadow-soft);
}
.date-fields { display: grid; grid-template-columns: 1fr auto 1fr; align-items: end; gap: .55rem; }
.date-fields label > span:first-child { display: block; margin-bottom: .35rem; color: var(--ink-soft); font-size: .8rem; font-weight: 700; }
.date-control { display: grid; grid-template-columns: minmax(0, 1fr) auto; }
.date-control input, .date-control select {
  min-width: 0;
  min-height: 3rem;
  padding: .6rem;
  border: 1px solid var(--line);
  background: var(--paper);
  color: var(--ink);
}
.date-control input { border-radius: .65rem 0 0 .65rem; }
.date-control select { border-left: 0; border-radius: 0 .65rem .65rem 0; }
.date-separator { padding-bottom: .75rem; color: var(--ink-soft); }
.field-note { margin: .65rem 0 0; color: var(--ink-soft); font-size: .82rem; }

.segmented-control {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  padding: .25rem;
  border: 1px solid var(--line);
  border-radius: .9rem;
  background: var(--surface);
}
.segmented-control input { position: absolute; opacity: 0; }
.segmented-control span {
  display: grid;
  min-height: 3rem;
  place-items: center;
  padding: .45rem;
  border-radius: .68rem;
  text-align: center;
  font-size: .78rem;
  font-weight: 750;
  cursor: pointer;
}
.segmented-control input:checked + span { background: var(--ink); color: var(--paper); }

.mode-cards { display: grid; gap: .65rem; }
.mode-cards label { cursor: pointer; }
.mode-cards input { position: absolute; opacity: 0; }
.mode-card {
  display: block;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 1.05rem;
  background: var(--surface);
  box-shadow: var(--shadow-soft);
}
.mode-card strong, .mode-card small { display: block; }
.mode-card small { margin-top: .25rem; color: var(--ink-soft); }
.mode-cards input:checked + .mode-card { border-color: var(--accent); box-shadow: inset 0 0 0 1px var(--accent); }

.quiz-panel { max-width: 44rem; margin: 0 auto; }
.quiz-topline { display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: .75rem; margin-bottom: 1rem; }
.text-button { display: inline-flex; min-height: 2.75rem; align-items: center; padding: .5rem .25rem; background: transparent; color: var(--ink-soft); }
.quiz-progress-track { overflow: hidden; height: .42rem; border-radius: 999px; background: var(--line); }
.quiz-progress-track span { display: block; width: 0; height: 100%; border-radius: inherit; background: var(--accent); transition: width .25s ease; }
.quiz-counter { color: var(--ink-soft); font-size: .82rem; font-variant-numeric: tabular-nums; }

.question-card {
  position: relative;
  overflow: hidden;
  padding: 1.1rem;
  border: 1px solid var(--line);
  border-radius: 1.45rem;
  background: var(--surface);
  box-shadow: var(--shadow);
}
.question-card::before { content: ""; position: absolute; inset: 0 0 auto; height: .32rem; background: var(--period-color); }
.question-meta { display: flex; align-items: center; justify-content: space-between; gap: .75rem; margin-bottom: 1.5rem; font-size: .78rem; }
.period-tag { padding: .28rem .55rem; border-radius: 999px; background: color-mix(in srgb, var(--period-color, var(--accent)) 14%, transparent); color: var(--period-color, var(--accent)); font-weight: 800; }
.question-card h2 { min-height: 4.3rem; margin-bottom: 1.35rem; font-size: clamp(1.5rem, 6.5vw, 2.35rem); font-weight: 820; }
.answer-options { display: grid; gap: .65rem; }
.answer-option {
  display: flex;
  width: 100%;
  min-height: 4.2rem;
  align-items: center;
  gap: .8rem;
  padding: .8rem;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: var(--paper);
  text-align: left;
  cursor: pointer;
  font-weight: 650;
  transition: transform .15s ease, border-color .15s ease, background .15s ease;
}
.answer-option .option-letter {
  display: grid;
  width: 2rem;
  height: 2rem;
  flex: 0 0 auto;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--surface);
  font-size: .78rem;
  font-weight: 800;
}
.answer-option:hover { border-color: var(--ink-soft); transform: translateY(-1px); }
.answer-option.is-correct { border-color: var(--success); background: color-mix(in srgb, var(--success) 11%, var(--surface)); }
.answer-option.is-wrong { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 10%, var(--surface)); }
.answer-option.is-correct { animation: correct-pop .32s ease; }
.answer-option.is-wrong { animation: wrong-shake .28s ease; }
.answer-option.is-selected { border-color: var(--accent); background: var(--accent-soft); }
.answer-option:disabled { color: var(--ink); cursor: default; }

@keyframes correct-pop { 50% { transform: scale(1.018); } }
@keyframes wrong-shake { 25% { transform: translateX(-4px); } 75% { transform: translateX(4px); } }

.answer-feedback { margin: 1rem 0; padding: 1rem; border-left: .25rem solid var(--success); border-radius: .25rem .75rem .75rem .25rem; background: color-mix(in srgb, var(--success) 9%, var(--paper)); }
.answer-feedback.is-wrong { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 8%, var(--paper)); }
.answer-feedback h3 { margin-bottom: .35rem; }
.answer-feedback > p:last-of-type { margin-bottom: 0; }
.typed-answer { display: grid; grid-template-columns: 1fr auto; gap: .65rem; width: 100%; }
.typed-answer, .matching-grid, .order-status { grid-column: 1 / -1; }
.typed-answer label span { display: block; margin-bottom: .3rem; color: var(--ink-soft); font-size: .78rem; font-weight: 750; }
.typed-answer input, .typed-answer select, .matching-grid select { width: 100%; min-height: 3.4rem; padding: .65rem; border: 1px solid var(--line); border-radius: .8rem; background: var(--paper); color: var(--ink); }
.order-status { margin-bottom: .15rem; color: var(--ink-soft); font-size: .8rem; }
.order-rank { display: grid; width: 2rem; height: 2rem; flex: 0 0 auto; place-items: center; border-radius: .65rem; background: var(--surface); color: var(--accent); font-weight: 850; }
.matching-grid { display: grid; gap: .75rem; width: 100%; }
.matching-grid label { display: grid; gap: .35rem; padding: .75rem; border: 1px solid var(--line); border-radius: .9rem; background: var(--paper); font-size: .86rem; font-weight: 700; }
.error-reasons { margin-top: .8rem; padding-top: .65rem; border-top: 1px solid var(--line); }
.error-reasons summary { color: var(--ink-soft); font-size: .78rem; font-weight: 750; cursor: pointer; }
.error-reasons div { display: flex; flex-wrap: wrap; gap: .45rem; margin-top: .55rem; }
.error-reasons button { padding: .45rem .65rem; border: 1px solid var(--line); border-radius: 999px; background: var(--surface); color: var(--ink); font-size: .74rem; cursor: pointer; }
.error-reasons button.is-selected { border-color: var(--accent); background: var(--accent-soft); }

.session-result { max-width: 40rem; margin: 1rem auto; text-align: center; }
.result-score {
  display: grid;
  width: 9rem;
  height: 9rem;
  margin: 1.4rem auto;
  place-content: center;
  border: .7rem solid color-mix(in srgb, var(--success) 35%, var(--line));
  border-radius: 50%;
}
.result-score strong { display: block; font-size: 2rem; }
.result-score small { color: var(--ink-soft); }
.result-actions { display: grid; gap: .7rem; margin-top: 1.5rem; }
.result-summary { display: grid; grid-template-columns: repeat(3, 1fr); gap: .55rem; margin: 1.2rem 0; }
.result-summary div { display: grid; gap: .15rem; padding: .75rem .4rem; border-radius: .85rem; background: var(--surface); box-shadow: var(--shadow-soft); }
.result-summary strong { font-size: .9rem; }
.result-summary span { color: var(--ink-soft); font-size: .68rem; }
.session-review { margin: 1rem 0; padding: 1rem; border: 1px solid var(--line); border-radius: 1rem; background: var(--surface); text-align: left; }
.session-review h2 { font-size: 1.15rem; }
.session-review div { display: grid; gap: .05rem; padding: .55rem 0; border-top: 1px solid var(--line); }
.session-review div span { color: var(--ink-soft); font-size: .78rem; }

.timeline-heading { display: flex; align-items: end; justify-content: space-between; gap: 1rem; }
.timeline-heading h1 { margin-bottom: 0; }
.timeline-filters { flex-wrap: nowrap; overflow-x: auto; padding-bottom: .25rem; scrollbar-width: none; }
.timeline-filters::-webkit-scrollbar { display: none; }
.timeline-range-panel { margin: 1rem 0; padding: .9rem; border: 1px solid var(--line); border-radius: 1rem; background: var(--surface); box-shadow: var(--shadow-soft); }
.range-toggle { min-height: 2.75rem; margin-top: .65rem; padding: .45rem 0; border: 0; background: transparent; color: var(--accent); font-weight: 800; cursor: pointer; }
.timeline-range-head, .timeline-range-actions { display: flex; align-items: center; justify-content: space-between; gap: .75rem; }
.timeline-range-head { margin-bottom: .45rem; font-size: .82rem; }
.timeline-range-head span { color: var(--ink-soft); font-variant-numeric: tabular-nums; }
.timeline-range-panel label { display: block; height: 1.4rem; }
.timeline-range-panel input[type="range"] { width: 100%; accent-color: var(--accent); }
.timeline-range-actions { margin-top: .55rem; }
.timeline-group-head { position: sticky; top: 4.2rem; z-index: 4; display: flex; align-items: center; justify-content: space-between; gap: .75rem; margin: 0 0 .9rem -.8rem; padding-right: .25rem; background: color-mix(in srgb, var(--paper) 90%, transparent); backdrop-filter: blur(10px); }
.timeline-group-head .timeline-group-title { position: static; margin: 0; background: transparent; backdrop-filter: none; }
.timeline-group-head .text-button { color: var(--period-color); font-size: .75rem; font-weight: 800; }
.search-field {
  display: flex;
  align-items: center;
  gap: .6rem;
  margin: 1rem 0 1.5rem;
  padding: 0 .85rem;
  border: 1px solid var(--line);
  border-radius: .85rem;
  background: var(--surface);
}
.search-field input { width: 100%; min-height: 3.2rem; border: 0; outline: 0; background: transparent; color: var(--ink); }

.timeline { position: relative; max-width: 52rem; margin: 0 auto; padding-left: 1.7rem; }
.timeline::before { content: ""; position: absolute; top: .5rem; bottom: .5rem; left: .36rem; width: 2px; background: var(--line); }
.timeline-group { margin-bottom: 2rem; }
.timeline-group-title { position: sticky; top: 4.2rem; z-index: 4; margin: 0 0 .9rem -.8rem; padding: .45rem .75rem; border-left: .28rem solid var(--period-color); background: color-mix(in srgb, var(--paper) 90%, transparent); backdrop-filter: blur(10px); }
.timeline-item { --period-color: var(--accent); position: relative; margin-bottom: .7rem; padding: .95rem; border: 1px solid var(--line); border-radius: 1.05rem; background: var(--surface); box-shadow: var(--shadow-soft); }
.timeline-gap { position: absolute; top: -.72rem; left: .8rem; padding: .05rem .35rem; border-radius: 999px; background: var(--paper); color: var(--ink-soft); font-size: .62rem; font-weight: 750; }
.timeline-item::before { content: ""; position: absolute; top: 1.15rem; left: -1.43rem; width: .65rem; height: .65rem; border: .2rem solid var(--paper); border-radius: 50%; background: var(--period-color); }
.timeline-item-date { display: block; margin: 0 0 .2rem; padding: 0; border: 0; background: transparent; color: var(--period-color); font-size: .82rem; font-weight: 850; cursor: pointer; }
.timeline-item h3 { margin: 0; font-family: inherit; font-size: 1rem; line-height: 1.4; letter-spacing: -.01em; }
.timeline-item p { margin: .45rem 0 0; color: var(--ink-soft); font-size: .82rem; }
.timeline-item .mastery-dot { position: absolute; top: .85rem; right: .85rem; width: .5rem; height: .5rem; border-radius: 50%; background: var(--line); }
.timeline-item .mastery-dot.learning { background: var(--warning); }
.timeline-item .mastery-dot.mastered { background: var(--success); }
.timeline.is-hidden-dates .timeline-item-date:not(.is-revealed) { filter: blur(.3rem); user-select: none; }
.mastery-label { display: inline-block; margin-top: .55rem; color: var(--ink-soft); font-size: .7rem; font-weight: 750; }
.timeline-empty { padding: 2rem; color: var(--ink-soft); text-align: center; }

.stats-overview { display: grid; grid-template-columns: repeat(2, 1fr); gap: .7rem; margin-bottom: 1rem; }
.stat-card { padding: 1rem; border: 1px solid var(--line); border-radius: 1.05rem; background: var(--surface); box-shadow: var(--shadow-soft); }
.stat-card strong { display: block; font-size: 1.6rem; line-height: 1.1; }
.stat-card span { color: var(--ink-soft); font-size: .78rem; }
.panel { margin-top: .8rem; padding: 1rem; border: 1px solid var(--line); border-radius: 1.2rem; background: var(--surface); box-shadow: var(--shadow-soft); }
.progress-details { margin-top: 1rem; }
.progress-details > summary { min-height: 3.2rem; padding: .8rem 1rem; border: 1px solid var(--line); border-radius: 1rem; background: var(--surface); font-weight: 800; cursor: pointer; }
.progress-details[open] > summary { border-color: var(--accent); color: var(--accent); }
.detail-stats { display: grid; grid-template-columns: repeat(2, 1fr); gap: .6rem; margin-top: .8rem; }
.detail-stats div { display: grid; padding: .75rem; border: 1px solid var(--line); border-radius: .85rem; background: var(--surface); }
.detail-stats span { color: var(--ink-soft); font-size: .72rem; }
.progress-insights { display: grid; gap: .8rem; }
.mastery-level { display: grid; grid-template-columns: 1fr auto; gap: .35rem .75rem; margin-bottom: .75rem; font-size: .8rem; }
.mastery-level .progress-bar { grid-column: 1 / -1; }
.mastery-level:nth-child(2) .progress-bar span { background: var(--danger); }
.mastery-level:nth-child(3) .progress-bar span { background: var(--warning); }
.mastery-level:nth-child(4) .progress-bar span { background: var(--success); }
.week-bars { display: grid; grid-template-columns: repeat(7, 1fr); align-items: end; gap: .3rem; min-height: 8rem; }
.week-bars > div { display: grid; justify-items: center; gap: .15rem; }
.week-bar { position: relative; width: .75rem; height: 4.6rem; overflow: hidden; border-radius: 999px; background: var(--line); }
.week-bar i { position: absolute; right: 0; bottom: 0; left: 0; border-radius: inherit; background: var(--accent); }
.week-bars strong, .week-bars small { font-size: .65rem; }
.week-bars small { color: var(--ink-soft); text-transform: capitalize; }
.weekly-summary p { margin: .75rem 0 0; color: var(--ink-soft); font-size: .78rem; text-align: center; }
.period-stat { margin-bottom: 1rem; }
.period-stat:last-child { margin-bottom: 0; }
.period-stat-head { display: flex; justify-content: space-between; gap: 1rem; margin-bottom: .4rem; font-size: .86rem; }
.period-stat-head strong:last-child { color: var(--period-color); }
.difficult-item, .history-item { display: grid; grid-template-columns: 1fr auto; gap: .75rem; padding: .75rem 0; border-top: 1px solid var(--line); }
.difficult-item:first-child, .history-item:first-child { border-top: 0; }
.difficult-item strong, .history-item strong { display: block; font-size: .88rem; }
.difficult-item small, .history-item small { color: var(--ink-soft); }
.difficulty-score { align-self: center; color: var(--danger); font-size: .8rem; font-weight: 800; }
.empty-state { display: grid; justify-items: center; gap: .35rem; padding: 1.25rem .75rem; color: var(--ink-soft); text-align: center; }
.empty-state strong { color: var(--ink); }
.empty-state span { max-width: 32rem; }
.empty-state .small-button { margin-top: .65rem; color: var(--ink); }

.data-tools { margin-top: 1rem; padding: 1rem; border: 1px solid var(--line); border-radius: 1rem; background: var(--surface); }
.data-tools summary { cursor: pointer; font-weight: 750; }
.data-tool-actions { display: grid; gap: .6rem; margin-top: 1rem; }
.file-action { position: relative; cursor: pointer; }
.file-action input { position: absolute; width: 1px; height: 1px; opacity: 0; }

.bottom-nav {
  position: fixed;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 40;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  padding: .45rem .35rem calc(.4rem + var(--safe-bottom));
  border-top: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 96%, transparent);
  box-shadow: 0 -8px 30px rgba(23, 50, 77, .07);
  backdrop-filter: blur(18px);
}
.bottom-nav button {
  display: grid;
  min-height: 3.4rem;
  place-items: center;
  gap: .08rem;
  border: 0;
  border-radius: .7rem;
  background: transparent;
  color: var(--ink-soft);
  font-size: .72rem;
  cursor: pointer;
}
.bottom-nav svg { width: 1.2rem; height: 1.2rem; }
.bottom-nav button.is-active { background: var(--accent-soft); color: var(--accent); font-weight: 850; }

.toast {
  position: fixed;
  right: 1rem;
  bottom: calc(5.5rem + var(--safe-bottom));
  left: 1rem;
  z-index: 60;
  max-width: 26rem;
  margin: auto;
  padding: .8rem 1rem;
  border-radius: .75rem;
  background: var(--ink);
  color: var(--paper);
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(1rem);
  pointer-events: none;
  transition: .2s ease;
}
.toast.is-visible { opacity: 1; transform: none; }

@media (min-width: 700px) {
  .topbar { padding-inline: max(1.5rem, calc((100% - 72rem) / 2)); }
  main { padding: 2rem 1.5rem 5rem; }
  .home-intro { align-items: center; padding: 1.8rem 2rem; }
  .mastery-ring { width: 7rem; height: 7rem; }
  .period-grid { grid-template-columns: repeat(2, 1fr); }
  .home-actions { grid-template-columns: repeat(2, 1fr); }
  .session-presets { grid-template-columns: repeat(3, 1fr); }
  .mode-cards { grid-template-columns: repeat(2, 1fr); }
  .question-card { padding: 1.7rem; }
  .answer-options { grid-template-columns: repeat(2, 1fr); }
  .stats-overview { grid-template-columns: repeat(4, 1fr); }
  .detail-stats { grid-template-columns: repeat(4, 1fr); }
  .progress-insights { grid-template-columns: repeat(2, 1fr); }
  .result-actions, .data-tool-actions { grid-template-columns: repeat(2, 1fr); }
  .timeline { display: block; padding-left: 2.25rem; }
  .timeline::before { display: block; left: .55rem; }
  .timeline-group { margin-bottom: 2.25rem; }
  .timeline-group-title { top: 4.55rem; margin-left: -1.1rem; }
  .timeline-item::before { display: block; left: -2.02rem; }
  .bottom-nav {
    position: fixed;
    bottom: 1rem;
    width: min(34rem, calc(100% - 2rem));
    margin: 0 auto 1rem;
    padding: .35rem;
    border: 1px solid var(--line);
    border-radius: 1rem;
  }
  .toast { bottom: 6rem; }
}

@media (min-width: 960px) {
  main { padding-top: 2.25rem; }
  .stats-overview { grid-template-columns: repeat(4, 1fr); }
  .bottom-nav {
    top: .45rem;
    bottom: auto;
    left: 50%;
    right: auto;
    width: 35rem;
    margin: 0;
    transform: translateX(-50%);
    box-shadow: none;
    background: transparent;
    border-color: transparent;
  }
  .bottom-nav button { min-height: 3.05rem; grid-template-columns: auto auto; justify-content: center; gap: .45rem; padding: 0 .8rem; }
  .bottom-nav button.is-active { background: var(--surface); box-shadow: var(--shadow-soft); }
  .toast { bottom: 1.25rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
}