:root {
  --ink: #090909;
  --paper: #fbfbf8;
  --surface: #ffffff;
  --soft: #efeee9;
  --accent: #c43a00;
  --muted: rgba(9, 9, 9, 0.56);
  --line: rgba(9, 9, 9, 0.22);
  --danger: #b42318;
  --gutter: clamp(20px, 3vw, 48px);
}

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

html {
  min-width: 320px;
  min-height: 100%;
  background: var(--paper);
}

body {
  min-height: 100svh;
  margin: 0;
  overflow-x: hidden;
  background: var(--paper);
  color: var(--ink);
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  -webkit-font-smoothing: antialiased;
}

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

button {
  cursor: pointer;
}

a {
  color: inherit;
  text-decoration: none;
}

[hidden] {
  display: none !important;
}

:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}

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

.flow-header {
  position: fixed;
  top: 0;
  right: 0;
  left: 0;
  z-index: 20;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  align-items: center;
  padding: 22px var(--gutter);
  background: linear-gradient(to bottom, var(--paper) 72%, rgba(251, 251, 248, 0));
}

.flow-wordmark {
  justify-self: start;
  font-size: 0.73rem;
  font-weight: 800;
  letter-spacing: 0.015em;
  text-transform: uppercase;
}

.flow-label {
  justify-self: center;
  color: var(--muted);
  font-size: 0.74rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.flow-language-switch {
  display: flex;
  align-items: center;
  justify-self: end;
  gap: 6px;
  padding: 4px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.72);
}

.language-choice {
  min-width: 54px;
  padding: 9px 13px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  font-size: 0.82rem;
}

.language-choice[aria-pressed="true"] {
  background: var(--ink);
  color: #fff;
}

.flow-shell {
  display: grid;
  width: min(100%, 1320px);
  min-height: 100svh;
  margin: 0 auto;
  grid-template-columns: minmax(0, 1fr) minmax(260px, 320px);
  align-items: center;
  gap: clamp(40px, 6vw, 96px);
  padding: 120px var(--gutter) 52px;
}

.signup-stage {
  width: min(100%, 760px);
}

.signup-login-cta {
  display: grid;
  min-height: 150px;
  padding: clamp(24px, 3vw, 34px);
  border: 3px solid var(--ink);
  border-radius: 22px;
  background: var(--ink);
  box-shadow: 8px 8px 0 #ff4b12;
  color: #fff;
  column-gap: 24px;
  grid-template-areas:
    "kicker arrow"
    "title arrow";
  grid-template-columns: minmax(0, 1fr) auto;
  grid-template-rows: auto 1fr;
  outline: none;
  transition: background 160ms ease, color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
}

.signup-login-kicker {
  align-self: end;
  color: #ff7040;
  font-size: clamp(0.82rem, 1.4vw, 0.95rem);
  font-weight: 800;
  grid-area: kicker;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.signup-login-title {
  min-width: 0;
  align-self: end;
  font-size: clamp(3rem, 6vw, 4.8rem);
  font-weight: 700;
  grid-area: title;
  letter-spacing: -0.065em;
  line-height: 0.9;
  white-space: nowrap;
}

.signup-login-arrow {
  display: grid;
  width: clamp(56px, 6vw, 68px);
  height: clamp(56px, 6vw, 68px);
  align-self: center;
  border-radius: 50%;
  background: #fff;
  color: var(--ink);
  font-size: clamp(1.65rem, 3vw, 2.1rem);
  grid-area: arrow;
  place-items: center;
}

.signup-login-cta:hover,
.signup-login-cta:focus-visible {
  background: #ff4b12;
  box-shadow: 8px 8px 0 var(--ink);
  color: var(--ink);
  transform: translate(-2px, -2px);
}

.signup-login-cta:hover .signup-login-kicker,
.signup-login-cta:focus-visible .signup-login-kicker {
  color: var(--ink);
}

.signup-login-divider {
  display: flex;
  align-items: center;
  gap: 16px;
  margin: clamp(28px, 4vw, 40px) 0;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.signup-login-divider::before,
.signup-login-divider::after {
  height: 1px;
  background: var(--line);
  content: "";
  flex: 1;
}

.signup-login-divider span {
  flex: 0 1 auto;
  text-align: center;
}

.progress-row {
  display: grid;
  margin-bottom: clamp(42px, 7vh, 74px);
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 18px;
}

.progress-track {
  height: 3px;
  overflow: hidden;
  background: rgba(9, 9, 9, 0.12);
}

.progress-value {
  width: 16.666%;
  height: 100%;
  background: var(--accent);
  transition: width 220ms ease;
}

.progress-label {
  margin: 0;
  color: var(--muted);
  font-size: 0.78rem;
  white-space: nowrap;
}

.question-step {
  min-height: 300px;
  border: 0;
  margin: 0;
  padding: 0;
  animation: question-in 220ms ease both;
}

@keyframes question-in {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.step-kicker {
  margin: 0 0 18px;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.06em;
}

.question-title {
  max-width: 760px;
  margin: 0 0 clamp(30px, 5vh, 48px);
  font-size: clamp(2.45rem, 5vw, 5.1rem);
  font-weight: 400;
  letter-spacing: -0.055em;
  line-height: 0.98;
}

.question-copy {
  max-width: 620px;
  margin: -24px 0 32px;
  color: var(--muted);
  font-size: clamp(1rem, 1.25vw, 1.15rem);
  line-height: 1.5;
}

.answer-input {
  width: 100%;
  min-height: 70px;
  padding: 14px 2px;
  border: 0;
  border-bottom: 2px solid var(--ink);
  border-radius: 0;
  outline: 0;
  background: transparent;
  font-size: clamp(1.7rem, 3vw, 2.7rem);
  letter-spacing: -0.035em;
  transition: border-color 160ms ease;
}

.answer-input::placeholder {
  color: rgba(9, 9, 9, 0.28);
  opacity: 1;
}

.answer-input:focus {
  border-color: var(--accent);
}

.answer-input[aria-invalid="true"] {
  border-color: var(--danger);
}

.field-note {
  max-width: 620px;
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 0.93rem;
  line-height: 1.45;
}

.field-error {
  min-height: 1.3em;
  margin: 12px 0 0;
  color: var(--danger);
  font-size: 0.9rem;
}

.form-navigation {
  display: flex;
  align-items: center;
  gap: 18px;
  margin-top: 28px;
}

.primary-action {
  display: inline-flex;
  min-height: 54px;
  align-items: center;
  justify-content: center;
  gap: 14px;
  padding: 14px 24px;
  border: 1.5px solid var(--ink);
  border-radius: 999px;
  background: var(--ink);
  color: #fff;
  font-weight: 700;
  transition: background 160ms ease, color 160ms ease, transform 160ms ease;
}

.primary-action:hover,
.primary-action:focus-visible {
  background: var(--accent);
  color: #fff;
}

.primary-action:active {
  transform: scale(0.98);
}

.key-hint {
  color: currentColor;
  font-size: 0.82em;
  opacity: 0.58;
}

.back-action {
  padding: 12px 4px;
  border: 0;
  background: transparent;
  color: var(--muted);
}

.back-action:hover,
.back-action:focus-visible {
  color: var(--ink);
}

.terms-summary {
  max-width: 680px;
  padding: clamp(20px, 3vw, 30px);
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--surface);
}

.terms-summary ul {
  display: grid;
  margin: 0;
  padding-left: 1.15em;
  gap: 12px;
}

.terms-summary li {
  padding-left: 5px;
  line-height: 1.45;
}

.terms-notice {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 0.82rem;
  line-height: 1.45;
}

.consent-list {
  display: grid;
  max-width: 680px;
  margin-top: 22px;
  gap: 12px;
}

.consent-option {
  display: grid;
  min-height: 62px;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.5);
  cursor: pointer;
  grid-template-columns: auto 1fr;
  align-items: start;
  gap: 13px;
  line-height: 1.42;
}

.consent-option:hover {
  border-color: var(--ink);
  background: var(--surface);
}

.consent-option input {
  width: 20px;
  height: 20px;
  margin: 1px 0 0;
  accent-color: var(--accent);
}

.help-aside {
  align-self: center;
}

.help-drawer {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.68);
}

.help-trigger {
  display: flex;
  min-height: 72px;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 20px 22px;
  cursor: pointer;
  font-size: 1.08rem;
  font-weight: 700;
  list-style: none;
}

.help-trigger::-webkit-details-marker {
  display: none;
}

.help-trigger::after {
  color: var(--accent);
  content: "+";
  font-size: 1.55rem;
  font-weight: 400;
}

.help-drawer[open] .help-trigger::after {
  content: "−";
}

.help-content {
  max-height: min(68vh, 650px);
  padding: 0 22px 24px;
  overflow-y: auto;
}

.help-title {
  margin: 8px 0 4px;
  font-size: 1.4rem;
  font-weight: 400;
  letter-spacing: -0.035em;
}

.help-subtitle {
  margin: 0 0 22px;
  color: var(--muted);
  font-size: 0.9rem;
}

.instruction-list {
  display: grid;
  margin: 0 0 24px;
  padding: 0;
  gap: 16px;
  list-style: none;
}

.instruction-list strong,
.instruction-list span {
  display: block;
}

.instruction-list strong {
  margin-bottom: 4px;
  font-size: 0.9rem;
}

.instruction-list span {
  color: var(--muted);
  font-size: 0.84rem;
  line-height: 1.4;
}

.faq-item {
  border-top: 1px solid var(--line);
}

.faq-item summary {
  padding: 16px 0;
  cursor: pointer;
  font-size: 0.87rem;
  font-weight: 700;
  line-height: 1.35;
}

.faq-item p {
  margin: -4px 0 16px;
  color: var(--muted);
  font-size: 0.84rem;
  line-height: 1.45;
}

.survey-shell {
  display: grid;
  min-height: 100svh;
  place-items: center;
  padding: 120px var(--gutter) 72px;
}

.survey-placeholder {
  width: min(100%, 820px);
}

.survey-eyebrow {
  margin: 0 0 22px;
  color: var(--accent);
  font-size: 0.84rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.survey-title {
  margin: 0 0 28px;
  font-size: clamp(3.2rem, 7vw, 7.6rem);
  font-weight: 400;
  letter-spacing: -0.065em;
  line-height: 0.91;
}

.survey-copy {
  max-width: 620px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(1.05rem, 1.6vw, 1.35rem);
  line-height: 1.5;
}

.confirmation-shell {
  display: grid;
  min-height: 100svh;
  justify-items: center;
  padding: 130px var(--gutter) 72px;
}

.confirmation-panel {
  width: min(100%, 1040px);
}

.confirmation-eyebrow,
.studies-eyebrow {
  margin: 0 0 20px;
  color: var(--accent);
  font-size: 0.84rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.confirmation-title {
  margin: 0 0 clamp(34px, 6vh, 64px);
  font-size: clamp(3.2rem, 7vw, 7.4rem);
  font-weight: 400;
  letter-spacing: -0.065em;
  line-height: 0.92;
}

.payment-card {
  padding: clamp(24px, 4vw, 44px);
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--surface);
}

.payment-copy {
  margin: 0;
  font-size: clamp(1.35rem, 2.4vw, 2.15rem);
  letter-spacing: -0.035em;
  line-height: 1.3;
}

.participant-email {
  color: var(--accent);
  overflow-wrap: anywhere;
}

.draft-notice {
  display: grid;
  margin-top: 28px;
  padding: 20px 22px;
  border: 1px solid rgba(180, 35, 24, 0.28);
  border-radius: 18px;
  background: #fff4f1;
  grid-template-columns: minmax(140px, 0.45fr) minmax(0, 1.55fr);
  gap: 22px;
}

.draft-notice strong {
  color: var(--danger);
  font-size: 0.84rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.draft-notice p {
  margin: 0;
  line-height: 1.5;
}

.terms-document {
  margin-top: 28px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--surface);
}

.terms-header {
  padding: clamp(28px, 5vw, 54px);
  border-bottom: 1px solid var(--line);
}

.terms-kicker {
  margin: 0 0 14px;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.terms-header h2 {
  max-width: 780px;
  margin: 0;
  font-size: clamp(2.2rem, 5vw, 4.8rem);
  font-weight: 400;
  letter-spacing: -0.055em;
  line-height: 0.96;
}

.terms-header > p:last-child {
  margin: 22px 0 0;
  color: var(--muted);
  font-size: 1rem;
}

.terms-section {
  padding: clamp(30px, 5vw, 54px);
}

.terms-section + .terms-section {
  border-top: 1px solid var(--line);
}

.terms-section h3 {
  display: flex;
  margin: 0 0 28px;
  align-items: center;
  gap: 14px;
  font-size: clamp(1.5rem, 2.5vw, 2.35rem);
  font-weight: 400;
  letter-spacing: -0.04em;
  line-height: 1.05;
}

.terms-section h3 span {
  display: inline-grid;
  width: 38px;
  height: 38px;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--ink);
  color: #fff;
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0;
  place-items: center;
}

.terms-section p,
.terms-section li,
.terms-section blockquote {
  max-width: 790px;
  font-size: clamp(1rem, 1.2vw, 1.12rem);
  line-height: 1.68;
}

.terms-section p {
  margin: 0 0 16px;
}

.terms-section p:last-child {
  margin-bottom: 0;
}

.terms-section ul {
  display: grid;
  max-width: 790px;
  margin: 0 0 20px;
  padding-left: 1.25em;
  gap: 8px;
}

.terms-section li {
  padding-left: 6px;
}

.terms-section blockquote {
  margin: 22px 0;
  padding: 22px 24px;
  border-left: 4px solid var(--accent);
  background: var(--soft);
}

.terms-section a {
  text-decoration: underline;
  text-decoration-color: var(--accent);
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}

.terms-placeholder {
  padding: 2px 5px;
  border-radius: 4px;
  background: #fff0b8;
  color: #5d3900;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.88em;
  font-weight: 700;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
}

.help-terms-section {
  background: #f4f7ff;
}

.terms-acceptance {
  margin-top: 28px;
  padding: clamp(26px, 4vw, 42px);
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--surface);
}

.terms-acceptance h2 {
  margin: 0 0 8px;
  font-size: clamp(1.8rem, 3vw, 2.8rem);
  font-weight: 400;
  letter-spacing: -0.045em;
}

.terms-acceptance > p:not(.field-error) {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.acceptance-list {
  max-width: none;
  margin-top: 26px;
}

.acceptance-list .consent-option {
  background: var(--paper);
}

.acceptance-list .optional-consent {
  border-style: dashed;
}

.acceptance-error {
  margin-bottom: 0;
}

.continue-studies {
  display: inline-flex;
  min-height: 58px;
  align-items: center;
  justify-content: center;
  gap: 14px;
  margin-top: 30px;
  padding: 15px 26px;
  border: 1.5px solid var(--ink);
  border-radius: 999px;
  background: var(--ink);
  color: #fff;
  font: inherit;
  font-weight: 700;
  transition: background 160ms ease, color 160ms ease;
}

.continue-studies:hover,
.continue-studies:focus-visible {
  background: var(--accent);
  color: #fff;
}

.account-pin-panel,
.login-help-card {
  margin-top: 26px;
  padding: clamp(20px, 3vw, 28px);
  border: 1px solid var(--line);
  border-radius: 20px;
  background: var(--paper);
}

.account-pin-panel h3,
.login-help-card h2 {
  margin: 0 0 8px;
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.025em;
}

.account-pin-panel > p,
.login-help-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.account-pin-fields {
  display: grid;
  margin-top: 20px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.account-pin-fields label {
  display: grid;
  gap: 8px;
  font-size: 0.84rem;
  font-weight: 700;
}

.account-pin-fields input {
  width: 100%;
  min-height: 54px;
  padding: 12px 16px;
  border: 1.5px solid var(--ink);
  border-radius: 12px;
  background: var(--surface);
  font: inherit;
  font-size: 1.15rem;
}

.account-pin-fields input:focus {
  border-color: var(--accent);
  outline: 3px solid color-mix(in srgb, var(--accent) 18%, transparent);
  outline-offset: 1px;
}

.account-pin-fields input[aria-invalid="true"] {
  border-color: var(--danger);
}

.login-instead-link,
.login-help-card a {
  display: inline-block;
  margin-top: 20px;
  border-bottom: 2px solid var(--accent);
  font-weight: 700;
  line-height: 1.45;
}

.login-instead-link {
  margin-left: 18px;
}

.login-help-card {
  margin-top: 0;
  background: var(--surface);
}

.login-help-card p + p {
  margin-top: 14px;
}

.studies-shell {
  width: min(100%, 1320px);
  min-height: 100svh;
  margin: 0 auto;
  padding: 140px var(--gutter) 72px;
}

.studies-header {
  max-width: 900px;
  margin-bottom: clamp(52px, 8vh, 96px);
}

.studies-title {
  margin: 0 0 24px;
  font-size: clamp(3.4rem, 7.8vw, 8.6rem);
  font-weight: 400;
  letter-spacing: -0.07em;
  line-height: 0.88;
}

.studies-intro {
  max-width: 660px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(1rem, 1.5vw, 1.24rem);
  line-height: 1.5;
}

.workspace-actions {
  display: flex;
  align-items: center;
  justify-self: end;
  gap: 12px;
}

.logout-button {
  padding: 9px 4px;
  border: 0;
  border-bottom: 1px solid var(--line);
  background: transparent;
  color: var(--muted);
  font-size: 0.82rem;
}

.logout-button:hover,
.logout-button:focus-visible {
  color: var(--ink);
}

.study-progress-panel {
  display: grid;
  margin-bottom: 34px;
  padding: clamp(22px, 3vw, 30px);
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--surface);
  grid-template-columns: minmax(0, 1fr) minmax(220px, 0.8fr);
  align-items: center;
  gap: 24px;
}

.study-progress-label {
  margin: 0 0 8px;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.study-progress-count {
  margin: 0;
  font-size: clamp(1.65rem, 3vw, 2.6rem);
  letter-spacing: -0.045em;
}

.study-progress-help {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.study-save-error {
  min-height: 1.3em;
  margin: -18px 0 22px;
  color: var(--danger);
  font-size: 0.9rem;
}

.study-list {
  border-top: 1px solid var(--line);
}

.study-empty-state {
  margin: 0;
  padding: 38px 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  color: var(--muted);
  font-size: 1rem;
  line-height: 1.5;
}

.study-card {
  display: grid;
  min-height: 150px;
  padding: 28px 0;
  border-bottom: 1px solid var(--line);
  grid-template-columns: 130px minmax(0, 1fr) auto;
  align-items: center;
  gap: clamp(22px, 4vw, 58px);
}

.study-code {
  margin: 0;
  color: var(--accent);
  font-size: 0.92rem;
  font-weight: 800;
  letter-spacing: 0.04em;
}

.study-check {
  display: inline-grid;
  width: 24px;
  height: 24px;
  margin-right: 10px;
  border: 1px solid currentColor;
  border-radius: 50%;
  place-items: center;
}

.study-card.is-clicked .study-check {
  background: var(--ink);
  color: #fff;
}

.study-card.is-clicked .study-code {
  color: var(--ink);
}

.study-name {
  margin: 0;
  font-size: clamp(2.4rem, 4.6vw, 5rem);
  font-weight: 400;
  letter-spacing: -0.055em;
  line-height: 0.94;
}

.study-link {
  display: inline-flex;
  min-width: 150px;
  min-height: 54px;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 13px 22px;
  border: 1.5px solid var(--ink);
  border-radius: 999px;
  background: transparent;
  font-size: 0.88rem;
  font-weight: 700;
  transition: background 160ms ease, color 160ms ease;
}

.study-link:hover,
.study-link:focus-visible {
  background: var(--ink);
  color: #fff;
}

[data-study-link][aria-disabled="true"] {
  pointer-events: none;
  opacity: 0.55;
}

.final-questionnaire-card {
  display: grid;
  margin-top: 44px;
  padding: clamp(26px, 4vw, 44px);
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--surface);
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 28px;
}

.final-questionnaire-card h2 {
  margin: 0 0 12px;
  font-size: clamp(2.2rem, 4.5vw, 4.5rem);
  font-weight: 400;
  letter-spacing: -0.055em;
  line-height: 0.95;
}

.final-questionnaire-card p:last-child {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.final-questionnaire-card.is-locked {
  background: var(--soft);
}

.final-questionnaire-card.is-locked p:last-child {
  color: rgba(9, 9, 9, 0.72);
}

.final-questionnaire-card.is-unlocked {
  border-color: var(--accent);
}

.final-questionnaire-card.is-complete {
  border-color: var(--ink);
}

.final-questionnaire-link[aria-disabled="true"] {
  cursor: not-allowed;
  opacity: 0.55;
}

.questionnaire-shell {
  display: grid;
  width: min(100%, 1100px);
  min-height: 100svh;
  margin: 0 auto;
  padding: 130px var(--gutter) 64px;
  align-items: center;
}

.questionnaire-stage {
  width: 100%;
}

.rating-step {
  min-height: 380px;
}

.rating-step legend {
  display: block;
  width: 100%;
  padding: 0;
}

.rating-step legend .step-kicker,
.rating-step legend .question-title {
  display: block;
}

.rating-scale {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 12px;
}

.rating-choice {
  position: relative;
  display: grid;
  min-height: 138px;
  padding: 18px 12px;
  border: 1.5px solid var(--line);
  border-radius: 18px;
  background: var(--surface);
  cursor: pointer;
  align-content: center;
  justify-items: center;
  gap: 12px;
  text-align: center;
  transition: border-color 160ms ease, background 160ms ease, color 160ms ease, transform 160ms ease;
}

.rating-choice:hover {
  border-color: var(--ink);
  transform: translateY(-2px);
}

.rating-choice:has(input:checked) {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.rating-choice:has(input:focus-visible) {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.rating-choice input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
}

.rating-number {
  font-size: 2.25rem;
  font-weight: 400;
  letter-spacing: -0.05em;
}

.rating-choice > span:last-child {
  font-size: 0.85rem;
  font-weight: 700;
  line-height: 1.25;
}

.questionnaire-error {
  margin-top: 8px;
}

.comments-step {
  min-height: 380px;
}

.comments-help {
  margin-top: -20px;
}

.comments-input {
  width: 100%;
  min-height: 210px;
  padding: 20px;
  resize: vertical;
  border: 1.5px solid var(--line);
  border-radius: 18px;
  outline: 0;
  background: var(--surface);
  font-size: 1.05rem;
  line-height: 1.55;
  transition: border-color 160ms ease, box-shadow 160ms ease;
}

.comments-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 16%, transparent);
}

.questionnaire-complete {
  width: 100%;
}

.completion-proof {
  margin-top: 44px;
  padding: clamp(22px, 4vw, 40px);
  border: 1px solid var(--line);
  border-radius: 28px;
  background: var(--surface);
}

.completion-proof-heading {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: end;
  gap: 28px;
  margin-bottom: 28px;
}

.completion-proof-kicker {
  margin: 0 0 8px;
  color: var(--accent);
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

.completion-proof h2 {
  margin: 0;
  font-size: clamp(1.8rem, 4vw, 3.6rem);
  font-weight: 400;
  letter-spacing: -0.05em;
  line-height: 1;
}

.completion-code-block {
  display: grid;
  justify-items: end;
  gap: 7px;
}

.completion-code-block span {
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.completion-code-block output {
  color: var(--accent);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: clamp(1rem, 2vw, 1.35rem);
  font-weight: 800;
  letter-spacing: 0.03em;
}

.confirmation-canvas {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: var(--paper);
}

.completion-proof-note {
  margin: 18px 0 0;
  color: var(--muted);
  line-height: 1.5;
}

.completion-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 24px;
}

.completion-actions .back-to-studies {
  margin-top: 0;
}

.copy-code-button {
  background: transparent;
  color: var(--ink);
  font: inherit;
  cursor: pointer;
}

.completion-actions button:disabled {
  cursor: wait;
  opacity: 0.5;
}

.copy-status {
  min-height: 1.3em;
  margin: 12px 0 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.back-to-studies {
  display: inline-flex;
  min-height: 54px;
  margin-top: 30px;
  padding: 14px 22px;
  border: 1.5px solid var(--ink);
  border-radius: 999px;
  align-items: center;
  font-weight: 700;
}

.back-to-studies:hover,
.back-to-studies:focus-visible {
  background: var(--ink);
  color: #fff;
}

.questionnaire-loading {
  color: var(--muted);
  font-size: 1rem;
}

@media (max-width: 960px) {
  .flow-shell {
    grid-template-columns: minmax(0, 1fr);
    align-content: center;
    gap: 36px;
  }

  .signup-stage {
    width: 100%;
  }

  .help-aside {
    width: min(100%, 760px);
  }

  .help-content {
    max-height: none;
  }
}

@media (max-width: 640px) {
  .flow-header {
    grid-template-columns: minmax(0, 1fr) auto;
    padding: 18px 20px;
  }

  .flow-wordmark {
    max-width: 76px;
    line-height: 1.05;
  }

  .flow-label {
    display: none;
  }

  .flow-language-switch {
    grid-column: 2;
  }

  .workspace-actions {
    grid-column: 2;
    gap: 8px;
  }

  .workspace-actions .flow-language-switch {
    grid-column: auto;
  }

  .logout-button {
    font-size: 0.75rem;
  }

  .language-choice {
    min-width: 48px;
    padding: 8px 11px;
  }

  .flow-shell {
    min-height: auto;
    align-content: start;
    padding: 112px 20px 36px;
  }

  .signup-login-cta {
    min-height: 140px;
    padding: 24px 22px;
    border-radius: 18px;
    box-shadow: 6px 6px 0 #ff4b12;
    column-gap: 16px;
  }

  .signup-login-title {
    font-size: clamp(2.8rem, 13vw, 3.4rem);
  }

  html[lang="zh-CN"] .signup-login-title {
    font-size: clamp(2.25rem, 11vw, 2.75rem);
    letter-spacing: -0.04em;
  }

  .signup-login-divider {
    margin: 30px 0;
    font-size: 0.7rem;
  }

  .progress-row {
    margin-bottom: 42px;
  }

  .question-step {
    min-height: 300px;
  }

  .question-title {
    font-size: clamp(2.35rem, 12vw, 3.5rem);
  }

  .question-copy {
    margin-top: -18px;
  }

  .answer-input {
    font-size: clamp(1.55rem, 8vw, 2.1rem);
  }

  .form-navigation {
    align-items: stretch;
    flex-direction: column;
  }

  .primary-action {
    width: 100%;
  }

  .back-action {
    order: 2;
  }

  .terms-summary {
    padding: 20px;
  }

  .account-pin-fields {
    grid-template-columns: minmax(0, 1fr);
  }

  .login-instead-link {
    display: table;
    margin: 20px auto 0;
  }

  .confirmation-shell,
  .studies-shell {
    padding: 116px 20px 40px;
  }

  .study-progress-panel,
  .final-questionnaire-card {
    grid-template-columns: minmax(0, 1fr);
  }

  .final-questionnaire-link {
    width: 100%;
  }

  .questionnaire-shell {
    min-height: auto;
    padding: 116px 20px 40px;
    align-items: start;
  }

  .rating-scale {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .rating-choice:last-child {
    grid-column: 1 / -1;
  }

  .completion-proof-heading {
    grid-template-columns: minmax(0, 1fr);
  }

  .completion-code-block {
    justify-items: start;
  }

  .completion-actions {
    align-items: stretch;
    flex-direction: column;
  }

  .completion-actions .primary-action,
  .completion-actions .back-to-studies {
    width: 100%;
  }

  .draft-notice {
    grid-template-columns: minmax(0, 1fr);
    gap: 8px;
  }

  .terms-section,
  .terms-header,
  .terms-acceptance {
    padding: 24px 20px;
  }

  .terms-section h3 {
    align-items: flex-start;
  }

  .terms-section blockquote {
    padding: 18px;
  }

  .continue-studies {
    width: 100%;
  }

  .study-card {
    grid-template-columns: minmax(0, 1fr);
    gap: 16px;
  }

  .study-link {
    width: 100%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .question-step,
  .progress-value {
    animation: none;
    transition: none;
  }
}