:root {
  --paper: #f3f8f9;
  --paper-solid: #f8fbfc;
  --ink: #152b38;
  --ink-soft: #49616e;
  --blue: #2457d6;
  --blue-dark: #163b9c;
  --aqua: #9ed9dc;
  --aqua-pale: #dceff0;
  --coral: #ee654d;
  --signal: #d7ed46;
  --line: #b8cdd2;
  --line-dark: #78939b;
  --white: #ffffff;
  --shadow: 0 18px 55px rgb(21 43 56 / 10%);
  --display: "Songti SC", "STSong", "Noto Serif CJK SC", serif;
  --body: "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --mono: "SFMono-Regular", "Cascadia Code", "Roboto Mono", monospace;
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: light;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--body);
  -webkit-font-smoothing: antialiased;
}

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

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--signal);
  outline-offset: 3px;
}

.grid-field {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background-image:
    linear-gradient(rgb(36 87 214 / 6%) 1px, transparent 1px),
    linear-gradient(90deg, rgb(36 87 214 / 6%) 1px, transparent 1px),
    linear-gradient(rgb(36 87 214 / 3%) 1px, transparent 1px),
    linear-gradient(90deg, rgb(36 87 214 / 3%) 1px, transparent 1px);
  background-size: 80px 80px, 80px 80px, 16px 16px, 16px 16px;
  mask-image: linear-gradient(to bottom, black 0%, transparent 90%);
}

[hidden] {
  display: none !important;
}

.welcome {
  width: min(1180px, calc(100% - 40px));
  min-height: 100vh;
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(240px, 0.62fr) minmax(0, 1.38fr);
  align-items: center;
  gap: clamp(44px, 8vw, 120px);
  padding: 56px 0;
}

.welcome-mark {
  position: relative;
  aspect-ratio: 1;
  display: grid;
  place-content: center;
  border: 2px solid var(--ink);
  background: var(--signal);
  box-shadow: 18px 18px 0 var(--blue);
  transform: rotate(-2.5deg);
}

.welcome-mark::before,
.welcome-mark::after {
  content: "";
  position: absolute;
  background: var(--ink);
}

.welcome-mark::before {
  width: 34%;
  height: 2px;
  top: 13%;
  left: -8%;
}

.welcome-mark::after {
  width: 2px;
  height: 28%;
  right: 12%;
  bottom: -8%;
}

.welcome-mark span {
  font: 700 clamp(7rem, 16vw, 12rem) / 0.78 var(--mono);
  letter-spacing: -0.12em;
  margin-left: -0.12em;
}

.welcome-mark small {
  margin-top: 28px;
  font: 700 0.78rem/1 var(--mono);
  letter-spacing: 0.2em;
  text-align: right;
}

.eyebrow,
.kicker,
.clock-label,
.rail-head,
.video-caption,
.evidence-card > span,
.assigned-claim > span,
.finish-grid span,
.followup-box > span {
  font: 700 0.7rem/1.4 var(--mono);
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.eyebrow,
.kicker {
  color: var(--blue);
}

.welcome h1 {
  max-width: 850px;
  margin: 18px 0 22px;
  font: 700 clamp(2.5rem, 6vw, 5.4rem) / 1.06 var(--display);
  letter-spacing: -0.045em;
  text-wrap: balance;
}

.lede {
  max-width: 720px;
  margin: 0 0 34px;
  color: var(--ink-soft);
  font-size: clamp(1rem, 1.7vw, 1.23rem);
  line-height: 1.85;
}

.start-form {
  display: grid;
  gap: 24px;
  max-width: 740px;
}

.mode-picker,
.scale-field,
.challenge-list,
.inline-choice {
  margin: 0;
  padding: 0;
  border: 0;
}

.mode-picker legend,
.scale-field legend,
.challenge-list legend,
.inline-choice legend {
  margin-bottom: 12px;
  font-weight: 700;
}

.mode-picker {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.mode-picker legend {
  grid-column: 1 / -1;
}

.mode-picker label {
  cursor: pointer;
}

.mode-picker input {
  position: absolute;
  opacity: 0;
}

.mode-picker label > span {
  min-height: 94px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 7px;
  padding: 16px 18px;
  border: 1px solid var(--line-dark);
  background: rgb(255 255 255 / 68%);
  transition: 160ms ease;
}

.mode-picker label > span small {
  color: var(--ink-soft);
  line-height: 1.5;
}

.mode-picker input:checked + span {
  border-color: var(--blue);
  box-shadow: inset 5px 0 0 var(--blue);
  background: var(--white);
}

.start-actions,
.export-actions,
.header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.privacy-note {
  margin: 20px 0 0;
  color: var(--ink-soft);
  font-size: 0.82rem;
}

.button,
.icon-button {
  min-height: 44px;
  border: 1px solid var(--ink);
  border-radius: 2px;
  padding: 0 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: var(--ink);
  background: transparent;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
  transition: transform 130ms ease, box-shadow 130ms ease, background 130ms ease;
}

.button:hover,
.icon-button:hover {
  transform: translateY(-2px);
}

.button.primary {
  color: var(--white);
  border-color: var(--blue);
  background: var(--blue);
  box-shadow: 5px 5px 0 var(--ink);
}

.button.primary:hover {
  box-shadow: 7px 7px 0 var(--ink);
}

.button.secondary {
  border-color: var(--blue);
  color: var(--blue-dark);
  background: var(--aqua-pale);
}

.button.ghost {
  border-color: var(--line-dark);
  background: rgb(255 255 255 / 65%);
}

.button.danger-ghost {
  color: #a73324;
  border-color: #d89d93;
}

.button:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.lab-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 292px minmax(0, 1fr);
  grid-template-rows: 72px minmax(0, 1fr);
}

.lab-header {
  position: sticky;
  top: 0;
  z-index: 20;
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 72px;
  padding: 0 24px;
  border-bottom: 1px solid var(--ink);
  background: rgb(248 251 252 / 94%);
  backdrop-filter: blur(14px);
}

.wordmark {
  width: fit-content;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  font-weight: 800;
  text-decoration: none;
}

.wordmark-square {
  width: 35px;
  height: 35px;
  display: grid;
  place-items: center;
  color: var(--white);
  background: var(--ink);
  font: 800 0.82rem/1 var(--mono);
}

.clock-cluster {
  display: flex;
  gap: 28px;
}

.clock-cluster > div {
  display: grid;
  grid-template-columns: auto auto;
  align-items: baseline;
  gap: 9px;
}

.clock-label {
  color: var(--ink-soft);
}

.clock {
  font: 700 1.3rem/1 var(--mono);
  font-variant-numeric: tabular-nums;
}

.clock.overdue {
  color: var(--coral);
}

.header-actions {
  justify-content: flex-end;
}

.save-status {
  color: var(--ink-soft);
  font: 600 0.75rem/1 var(--mono);
}

.icon-button {
  min-height: 34px;
  padding: 0 12px;
  border-color: var(--line-dark);
  font-size: 0.78rem;
}

.evidence-rail {
  position: sticky;
  top: 72px;
  height: calc(100vh - 72px);
  overflow: auto;
  border-right: 1px solid var(--ink);
  background: var(--ink);
  color: var(--white);
}

.rail-head {
  position: sticky;
  top: 0;
  z-index: 2;
  display: flex;
  justify-content: space-between;
  padding: 20px 20px 14px;
  color: var(--aqua);
  background: var(--ink);
}

#phase-rail {
  position: relative;
  padding: 4px 14px 30px 24px;
}

#phase-rail::before {
  content: "";
  position: absolute;
  top: 20px;
  bottom: 46px;
  left: 33px;
  width: 1px;
  background: rgb(255 255 255 / 24%);
}

.rail-item {
  position: relative;
  width: 100%;
  min-height: 57px;
  display: grid;
  grid-template-columns: 20px minmax(0, 1fr);
  align-items: center;
  gap: 14px;
  padding: 7px 10px 7px 0;
  border: 0;
  color: rgb(255 255 255 / 58%);
  background: transparent;
  text-align: left;
  cursor: pointer;
}

.rail-dot {
  position: relative;
  z-index: 1;
  width: 18px;
  height: 18px;
  display: grid;
  place-items: center;
  border: 1px solid rgb(255 255 255 / 45%);
  background: var(--ink);
  font: 700 0.55rem/1 var(--mono);
}

.rail-item span:last-child {
  display: grid;
  gap: 3px;
}

.rail-item strong {
  font-size: 0.84rem;
}

.rail-item small {
  color: inherit;
  font: 500 0.64rem/1 var(--mono);
}

.rail-item.current {
  color: var(--white);
}

.rail-item.current .rail-dot {
  color: var(--ink);
  border-color: var(--signal);
  background: var(--signal);
  box-shadow: 0 0 0 5px rgb(215 237 70 / 16%);
}

.rail-item.visited:not(.current) .rail-dot {
  color: var(--ink);
  border-color: var(--aqua);
  background: var(--aqua);
}

.lab-main {
  width: min(940px, calc(100% - 64px));
  margin: 0 auto;
  padding: 46px 0 120px;
}

.phase-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line-dark);
}

.phase-meta .eyebrow {
  margin: 0;
}

.phase-rule {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.82rem;
}

.phase {
  position: relative;
  min-height: 560px;
  padding: clamp(28px, 5vw, 56px);
  border: 1px solid var(--ink);
  background: rgb(248 251 252 / 96%);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.phase-number {
  position: absolute;
  top: -0.18em;
  right: 0.06em;
  z-index: 0;
  color: rgb(36 87 214 / 7%);
  font: 800 clamp(8rem, 22vw, 15rem) / 1 var(--mono);
  letter-spacing: -0.12em;
  pointer-events: none;
}

.phase > *:not(.phase-number) {
  position: relative;
  z-index: 1;
}

.kicker {
  margin: 0 0 10px;
}

.phase h2 {
  max-width: 760px;
  margin: 0 0 16px;
  font: 700 clamp(2rem, 4.2vw, 3.7rem) / 1.12 var(--display);
  letter-spacing: -0.035em;
}

.final-phase h2 {
  font-size: clamp(2rem, 3.5vw, 3.25rem);
}

.intro {
  max-width: 700px;
  margin: 0 0 30px;
  color: var(--ink-soft);
  font-size: 1rem;
  line-height: 1.8;
}

.field {
  display: grid;
  gap: 8px;
  margin: 22px 0;
}

.field > span,
.task-line {
  font-size: 0.92rem;
  font-weight: 700;
  line-height: 1.65;
}

.compact-field {
  max-width: 440px;
}

input,
textarea,
select {
  width: 100%;
  border: 1px solid var(--line-dark);
  border-radius: 2px;
  color: var(--ink);
  background: var(--white);
}

input,
select {
  min-height: 46px;
  padding: 0 13px;
}

textarea {
  min-height: 78px;
  padding: 12px 13px;
  line-height: 1.65;
  resize: vertical;
}

input:hover,
textarea:hover,
select:hover {
  border-color: var(--blue);
}

.number-scale {
  display: grid;
  grid-template-columns: repeat(5, 54px);
  gap: 8px;
}

.number-scale label {
  cursor: pointer;
}

.number-scale input {
  position: absolute;
  opacity: 0;
  width: 0;
  min-height: 0;
}

.number-scale span {
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line-dark);
  background: var(--white);
  font: 700 1rem/1 var(--mono);
}

.number-scale input:checked + span {
  color: var(--white);
  border-color: var(--blue);
  background: var(--blue);
}

.video-frame {
  margin: 28px 0;
  border: 1px solid var(--ink);
  background: #050708;
}

.video-frame video {
  width: 100%;
  display: block;
  aspect-ratio: 16 / 9;
  object-fit: contain;
}

.video-caption {
  display: flex;
  justify-content: space-between;
  padding: 10px 13px;
  color: var(--aqua);
  border-top: 1px solid var(--line-dark);
}

.keyword-grid,
.packet-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0 20px;
}

.scenario,
.concept-note,
.assigned-claim,
.followup-box {
  margin: 24px 0;
  padding: 22px 24px;
  border-left: 6px solid var(--blue);
  background: var(--aqua-pale);
  font: 600 1rem/1.8 var(--body);
}

.scenario.compact {
  padding: 16px 18px;
  font-size: 0.92rem;
}

.claim-scenario {
  border-color: var(--coral);
  background: #fbe7e2;
  font-family: var(--display);
  font-size: 1.3rem;
}

.assist-check,
.choice-line {
  width: fit-content;
  display: inline-flex;
  align-items: center;
  gap: 9px;
  margin-top: 8px;
  color: var(--ink-soft);
  cursor: pointer;
}

.assist-check input,
.choice-line input,
.challenge-list input,
.inline-choice input {
  width: 18px;
  min-height: 18px;
  accent-color: var(--blue);
}

.branch-picker {
  display: inline-flex;
  margin: 16px 0 24px;
  border: 1px solid var(--ink);
}

.branch {
  min-height: 42px;
  padding: 0 22px;
  border: 0;
  color: var(--ink);
  background: transparent;
  font-weight: 700;
  cursor: pointer;
}

.branch + .branch {
  border-left: 1px solid var(--ink);
}

.branch.active {
  color: var(--white);
  background: var(--ink);
}

.action-strip {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 18px;
  border: 1px solid var(--line-dark);
  background: var(--white);
}

.action-strip > div {
  display: grid;
  gap: 5px;
}

.action-strip span {
  color: var(--ink-soft);
  font-size: 0.86rem;
}

.procedure {
  margin: 24px 0;
  padding-left: 1.4rem;
}

.procedure li {
  margin: 10px 0;
  padding-left: 5px;
  line-height: 1.65;
}

.deadline-note {
  padding: 12px 14px;
  color: #71291e;
  border: 1px solid #e3a79c;
  background: #fceae6;
  font-size: 0.87rem;
}

.deadline-note span {
  font: 800 0.9rem/1 var(--mono);
}

.result-table-wrap {
  margin: 24px 0;
  overflow-x: auto;
}

.result-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--white);
}

.result-table th,
.result-table td {
  padding: 13px 12px;
  border: 1px solid var(--line-dark);
  text-align: left;
}

.result-table th {
  font-size: 0.82rem;
}

.result-table select {
  min-width: 110px;
}

.compare-grid {
  display: grid;
  grid-template-columns: 0.72fr 1.28fr;
  gap: 16px;
  margin: 26px 0;
}

.compare-grid article,
.evidence-card {
  padding: 20px;
  border: 1px solid var(--line-dark);
  background: var(--white);
}

.compare-grid article > span {
  color: var(--blue);
  font: 700 0.72rem/1 var(--mono);
}

.compare-grid p {
  line-height: 1.75;
}

.material-note {
  padding-top: 12px;
  border-top: 1px dashed var(--line-dark);
  color: var(--ink-soft);
  font-size: 0.87rem;
}

.concept-note strong {
  font: 800 0.74rem/1 var(--mono);
  letter-spacing: 0.08em;
}

.concept-note p {
  margin: 5px 0 0;
  font-weight: 500;
}

.source-cards {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin: 24px 0;
  padding: 0;
  list-style: none;
}

.source-cards li {
  min-height: 104px;
  padding: 16px;
  border: 1px solid var(--line-dark);
  background: var(--white);
  line-height: 1.65;
}

.source-cards b {
  display: block;
  margin-bottom: 8px;
  color: var(--blue);
  font: 800 0.75rem/1 var(--mono);
}

.taxonomy {
  margin: 24px 0;
  border: 1px solid var(--line-dark);
  background: var(--white);
}

.taxonomy summary {
  padding: 15px 18px;
  font-weight: 800;
  cursor: pointer;
}

.taxonomy ol {
  margin: 0;
  padding: 0 28px 18px 42px;
}

.taxonomy li {
  margin: 8px 0;
  line-height: 1.55;
}

.evidence-card {
  margin: 12px 0;
}

.evidence-card > span {
  color: var(--blue);
}

.evidence-card p {
  margin: 10px 0 0;
  line-height: 1.75;
}

.assigned-claim {
  display: grid;
  gap: 7px;
  border-color: var(--coral);
  background: #fbe7e2;
}

.assigned-claim > span {
  color: #a23b2b;
}

.assigned-claim strong {
  font: 700 1.18rem/1.6 var(--display);
}

.challenge-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin: 24px 0;
}

.challenge-list legend {
  grid-column: 1 / -1;
}

.challenge-list label,
.inline-choice label {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px;
  border: 1px solid var(--line-dark);
  background: var(--white);
  cursor: pointer;
}

.inline-choice {
  display: flex;
  align-items: center;
  gap: 9px;
  flex-wrap: wrap;
  margin: 22px 0;
}

.inline-choice legend {
  width: 100%;
}

.inline-choice label {
  min-width: 92px;
}

.optional-field {
  opacity: 0.82;
}

.finish-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin: 30px 0;
}

.finish-grid article {
  display: grid;
  gap: 12px;
  min-height: 118px;
  padding: 18px;
  border: 1px solid var(--line-dark);
  background: var(--white);
}

.finish-grid span {
  color: var(--ink-soft);
}

.finish-grid strong {
  align-self: end;
  font: 700 1.45rem/1.15 var(--mono);
}

.followup-box {
  margin-top: 34px;
  border-color: var(--signal);
  background: #f4f9cc;
}

.followup-box p {
  margin: 7px 0 0;
  font-weight: 500;
}

.phase-controls {
  position: fixed;
  right: 0;
  bottom: 0;
  left: 292px;
  z-index: 15;
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 20px;
  min-height: 76px;
  padding: 12px max(28px, calc((100vw - 292px - 940px) / 2));
  border-top: 1px solid var(--ink);
  background: rgb(248 251 252 / 96%);
  backdrop-filter: blur(14px);
}

.phase-controls p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.78rem;
  text-align: center;
}

.toast {
  position: fixed;
  right: 24px;
  bottom: 94px;
  z-index: 40;
  max-width: 340px;
  padding: 13px 16px;
  color: var(--white);
  background: var(--ink);
  box-shadow: 7px 7px 0 var(--signal);
  transform: translateY(20px);
  opacity: 0;
  pointer-events: none;
  transition: 180ms ease;
}

.toast.show {
  transform: translateY(0);
  opacity: 1;
}

@media (max-width: 980px) {
  .welcome {
    grid-template-columns: 1fr;
    align-content: center;
  }

  .welcome-mark {
    width: min(270px, 68vw);
  }

  .lab-shell {
    display: block;
    padding-top: 72px;
  }

  .lab-header {
    position: fixed;
    right: 0;
    left: 0;
    grid-template-columns: auto 1fr auto;
  }

  .save-status,
  .phase-clock,
  .clock-cluster > div:nth-child(2),
  .wordmark > span:last-child {
    display: none;
  }

  .clock-cluster {
    justify-self: center;
  }

  .evidence-rail {
    position: sticky;
    top: 72px;
    z-index: 12;
    width: 100%;
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }

  .rail-head {
    display: none;
  }

  #phase-rail {
    display: flex;
    padding: 8px 14px;
    overflow-x: auto;
  }

  #phase-rail::before {
    display: none;
  }

  .rail-item {
    width: auto;
    min-width: 46px;
    min-height: 42px;
    grid-template-columns: 1fr;
    padding: 4px;
  }

  .rail-item span:last-child {
    display: none;
  }

  .rail-dot {
    width: 32px;
    height: 32px;
  }

  .lab-main {
    width: min(880px, calc(100% - 36px));
    padding-top: 28px;
    scroll-margin-top: 148px;
  }

  .phase-controls {
    left: 0;
    padding: 12px 18px;
  }
}

@media (max-width: 680px) {
  .welcome {
    width: min(100% - 28px, 580px);
    padding: 28px 0 60px;
  }

  .welcome h1 {
    font-size: clamp(2.25rem, 12vw, 3.7rem);
  }

  .mode-picker,
  .keyword-grid,
  .packet-grid,
  .compare-grid,
  .source-cards,
  .challenge-list,
  .finish-grid {
    grid-template-columns: 1fr;
  }

  .lab-header {
    padding: 0 14px;
  }

  .lab-main {
    width: calc(100% - 20px);
  }

  .phase {
    min-height: 520px;
    padding: 26px 18px 34px;
  }

  .phase h2 {
    font-size: 2rem;
  }

  .phase-meta {
    align-items: flex-start;
    flex-direction: column;
    gap: 6px;
  }

  .number-scale {
    grid-template-columns: repeat(5, 1fr);
  }

  .number-scale span {
    width: 100%;
    height: 48px;
  }

  .action-strip {
    align-items: stretch;
    flex-direction: column;
  }

  .result-table th,
  .result-table td {
    padding: 10px 8px;
    font-size: 0.78rem;
  }

  .phase-controls {
    grid-template-columns: 1fr 1fr;
    gap: 10px;
  }

  .phase-controls p {
    display: none;
  }

  .export-actions .button {
    width: 100%;
  }

  .toast {
    right: 14px;
    bottom: 92px;
    left: 14px;
    max-width: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.001ms !important;
    animation-duration: 0.001ms !important;
  }
}

@media print {
  .grid-field,
  .lab-header,
  .evidence-rail,
  .phase-controls,
  .toast,
  .welcome {
    display: none !important;
  }

  .lab-shell,
  .lab-main,
  .phase {
    display: block !important;
    width: 100%;
    min-height: 0;
    margin: 0;
    padding: 0;
    border: 0;
    box-shadow: none;
  }

  .phase[hidden] {
    display: none !important;
  }
}