:root {
  --bg: #ffffff;
  --surface: #ffffff;
  --text: #1f1f1f;
  --text-soft: #3f3f3f;
  --muted: #6e6e6e;
  --border: #e5e5e5;
  --border-soft: #ededed;
  --accent: #2563eb;
  --accent-strong: #1d4ed8;
  --accent-soft: #eef4ff;
  --user-bubble: #f3ebdc;
  --user-text: #1f1f1f;
  --assistant-text: #1f1f1f;
  --sponsored-bg: #faf9f6;
  --sponsored-border: #ececec;
  --shadow: 0 1px 2px rgba(0,0,0,0.04);
  --max-width: 760px;
  --font-sans: "Inter", ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
               "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0;
  height: 100%;
  font-family: var(--font-sans);
  color: var(--text);
  background: var(--bg);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
body { display: flex; flex-direction: column; min-height: 100vh; }

/* ===== Screen toggling ===== */
.screen { display: none; }
body[data-screen="prolific"] #screen-prolific { display: block; }
body[data-screen="consent"]  #screen-consent { display: block; }
body[data-screen="welcome"]  #screen-welcome { display: block; }
body[data-screen="chat"]     #screen-chat,
body[data-screen="chat"]     .composer { display: flex; }
body[data-screen="chat"]     #screen-chat { display: flex; }
body[data-screen="postsurvey"] #screen-postsurvey { display: block; }
body[data-screen="recall"]   #screen-recall { display: block; }
body[data-screen="relevance"] #screen-relevance { display: block; }
body[data-screen="thanks"]   #screen-thanks { display: block; }
body[data-screen="declined"] #screen-declined { display: block; }
.composer { display: none; }

/* ===== Top bar ===== */
.topbar {
  position: sticky; top: 0; z-index: 10;
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 10px 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.brand {
  display: flex; align-items: center; gap: 8px;
  font-weight: 600; font-size: 15px; letter-spacing: -0.1px;
}
.brand-name { color: var(--text); }
.topbar-right { display: flex; align-items: center; gap: 8px; }
.session-tag {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 11px; color: var(--muted);
  background: #f3f4f6;
  padding: 3px 7px; border-radius: 999px;
}
.arm-badge, .topic-badge {
  font-size: 10px; font-weight: 600; letter-spacing: 0.4px; text-transform: uppercase;
  color: #2563eb; background: var(--accent-soft); border: 1px solid #c7d6f3;
  padding: 3px 8px; border-radius: 999px;
}
.arm-badge[data-arm="ads-neutral"]      { color: #6b7280; background: #f3f4f6; border-color: #e5e7eb; }
.arm-badge[data-arm="ads-personalized"] { color: #8a4f0a; background: #fef3c7; border-color: #fde68a; }
.arm-badge[data-arm="ads-character"]    { color: #7a2f5a; background: #fbe6f1; border-color: #f3c8e1; }
.topic-badge { color: #3a4f7a; background: #e6ecf5; border-color: #c3d2e5; }

.next-btn {
  background: var(--accent); color: #ffffff;
  border: none; padding: 7px 14px; border-radius: 999px;
  font: inherit; font-size: 13px; font-weight: 600;
  cursor: pointer; transition: background 0.15s ease, opacity 0.15s ease;
}
.next-btn:hover:not(:disabled) { background: var(--accent-strong); }
.next-btn:disabled { background: #d1d5db; color: #ffffff; cursor: not-allowed; opacity: 0.6; }

.composer-row {
  width: 100%;
  max-width: var(--max-width);
  display: flex;
  align-items: flex-end;
  gap: 10px;
}
.composer-row .composer-inner { flex: 1; }
.composer-next-btn {
  flex-shrink: 0;
  background: var(--accent); color: #ffffff;
  border: none; padding: 0 18px; height: 46px; border-radius: 999px;
  font: inherit; font-size: 14px; font-weight: 600;
  cursor: pointer; transition: background 0.15s ease, opacity 0.15s ease;
  white-space: nowrap;
}
.composer-next-btn:hover:not(:disabled) { background: var(--accent-strong); }
.composer-next-btn:disabled {
  background: #d1d5db; color: #ffffff;
  cursor: not-allowed; opacity: 0.65;
}

.primary-btn {
  background: var(--accent); color: #ffffff;
  border: none; padding: 11px 22px; border-radius: 10px;
  font: inherit; font-size: 15px; font-weight: 600;
  cursor: pointer; transition: background 0.15s ease;
}
.primary-btn:hover:not(:disabled) { background: var(--accent-strong); }
.primary-btn:disabled { background: #d1d5db; cursor: not-allowed; }

/* ===== Cards / screens ===== */
.screen-welcome, .screen-postsurvey, .screen-recall, .screen-thanks { padding: 32px 18px 60px; }
.card {
  max-width: 560px; margin: 0 auto;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 28px 28px;
  box-shadow: var(--shadow);
}
.card-wide { max-width: 720px; }
.card h1 { font-size: 24px; font-weight: 600; margin: 0 0 6px; letter-spacing: -0.3px; }
.card h2 { font-size: 15px; font-weight: 600; margin: 0 0 8px; color: var(--text); }
.card .lede { color: var(--text-soft); font-size: 15px; margin: 0 0 18px; }
.task-box {
  background: #fafafa; border: 1px solid var(--border-soft); border-radius: 10px;
  padding: 14px 18px; margin-bottom: 22px;
}
.task-box ol { margin: 6px 0 0; padding-left: 20px; color: var(--text-soft); font-size: 14px; }
.task-box li { margin: 3px 0; }
.tiny { font-size: 12px; color: var(--muted); margin-top: 16px; text-align: center; }
.tiny code { background: #f3f4f6; padding: 2px 5px; border-radius: 4px; font-size: 11px; }
.muted-small { font-size: 13px; color: var(--muted); }
.big-frog { text-align: center; margin: 0 auto 8px; }
.debrief { background: #fafafa; border: 1px solid var(--border-soft); border-radius: 10px;
           padding: 14px 18px; margin: 14px 0 6px; }
.debrief h2 { margin-top: 0; }
.debrief p { margin: 6px 0; color: var(--text-soft); font-size: 14px; }

/* ===== Survey items ===== */
.q-item {
  background: #fafafa;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  padding: 14px 16px;
  margin-bottom: 14px;
}
.q-item-text {
  font-size: 15px; font-weight: 600; color: var(--text);
  margin: 0 0 10px;
  line-height: 1.45;
}
.q-item-help {
  font-size: 12.5px; color: var(--muted);
  margin: -4px 0 10px;
}
.q-likert {
  display: grid; gap: 4px;
  grid-template-columns: 1fr;
}
.q-likert-labels {
  display: flex; justify-content: space-between;
  font-size: 11.5px; color: var(--muted); padding: 0 2px;
}
.q-likert-options {
  display: grid; gap: 4px;
  margin: 4px 0 2px;
}
.q-likert[data-scale="5"] .q-likert-options { grid-template-columns: repeat(5, 1fr); }
.q-likert[data-scale="7"] .q-likert-options { grid-template-columns: repeat(7, 1fr); }
.q-likert[data-scale="3"] .q-likert-options { grid-template-columns: repeat(3, 1fr); }
.q-likert-options label {
  display: flex; flex-direction: column; align-items: center;
  gap: 4px; padding: 6px 4px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  font-size: 12.5px; color: var(--text);
  user-select: none;
  transition: border-color 0.12s ease, background 0.12s ease;
}
.q-likert-options label:hover { border-color: var(--accent); }
.q-likert-options label.is-selected {
  border-color: var(--accent);
  background: var(--accent-soft);
  font-weight: 600;
}
.q-likert-options input[type="radio"] {
  position: absolute; opacity: 0; pointer-events: none;
}
.q-likert-options .q-likert-value { font-weight: 600; font-size: 13px; }
.q-likert-options .q-likert-mini-label {
  font-size: 10.5px; color: var(--muted); line-height: 1.2;
  text-align: center;
}
.q-open-text textarea,
.q-open-text input {
  width: 100%;
  font: inherit; font-size: 14px;
  padding: 10px 12px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  resize: vertical;
  min-height: 56px;
}
.q-select select {
  width: 100%;
  font: inherit; font-size: 14px;
  padding: 9px 12px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
}
.q-yes-no, .q-yes-no-notsure { display: flex; gap: 8px; flex-wrap: wrap; }
.q-yes-no label, .q-yes-no-notsure label {
  flex: 1; min-width: 80px;
  padding: 10px; background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  text-align: center;
  font-size: 14px;
  cursor: pointer;
  user-select: none;
  transition: border-color 0.12s ease, background 0.12s ease;
}
.q-yes-no label.is-selected,
.q-yes-no-notsure label.is-selected {
  border-color: var(--accent);
  background: var(--accent-soft);
  font-weight: 600;
}
.q-yes-no input[type="radio"],
.q-yes-no-notsure input[type="radio"] {
  position: absolute; opacity: 0; pointer-events: none;
}
.q-numeric input {
  width: 200px;
  font: inherit; font-size: 14px;
  padding: 9px 12px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
}
.q-numeric .q-numeric-suffix {
  font-size: 13px; color: var(--muted); margin-left: 8px;
}
.q-conditional { display: none; }
.q-conditional.is-visible { display: block; }

/* ===== Slider ===== */
.survey-block { margin-bottom: 20px; }
.survey-question { font-size: 16px !important; margin: 0 0 4px !important; color: var(--text) !important; font-weight: 600; }
.survey-help { color: var(--muted); margin: 0 0 14px; font-size: 13px; }
.slider-wrap { background: #fafafa; border: 1px solid var(--border-soft); border-radius: 10px; padding: 14px 16px 12px; }
.slider-labels { display: flex; justify-content: space-between; font-size: 12px; color: var(--muted); margin-bottom: 8px; }
.trust-slider {
  appearance: none; -webkit-appearance: none; width: 100%;
  height: 6px; border-radius: 999px;
  background: linear-gradient(90deg, #f0d6d6 0%, #f5e6c0 50%, #cfe9d8 100%);
  outline: none; margin: 6px 0 4px;
}
.trust-slider::-webkit-slider-thumb {
  appearance: none; -webkit-appearance: none;
  width: 22px; height: 22px; border-radius: 50%;
  background: #fff; border: 2px solid var(--accent);
  box-shadow: 0 1px 4px rgba(0,0,0,0.15); cursor: pointer; opacity: 0;
  transition: opacity 0.15s ease, transform 0.1s ease;
}
.trust-slider::-moz-range-thumb {
  width: 22px; height: 22px; border-radius: 50%;
  background: #fff; border: 2px solid var(--accent);
  box-shadow: 0 1px 4px rgba(0,0,0,0.15); cursor: pointer; opacity: 0;
}
.trust-slider[data-touched="true"]::-webkit-slider-thumb { opacity: 1; }
.trust-slider[data-touched="true"]::-moz-range-thumb { opacity: 1; }
.slider-ticks { display: flex; justify-content: space-between; font-size: 11px; color: var(--muted); padding: 0 10px; margin-top: 1px; }
.slider-readout { margin-top: 10px; text-align: center; font-size: 13px; color: var(--text-soft); }
.slider-readout strong { color: var(--accent-strong); font-size: 16px; }

/* ===== Chat ===== */
.screen-chat {
  flex: 1; width: 100%;
  justify-content: center;
  padding: 18px 18px 130px;
}
.chat-inner { width: 100%; max-width: var(--max-width); margin: 0 auto; }
.messages { display: flex; flex-direction: column; gap: 16px; }

.msg { display: flex; width: 100%; }
.msg.user { justify-content: flex-end; }
.msg.assistant, .msg.system { justify-content: flex-start; }

/* User: soft beige bubble */
.msg.user .bubble {
  background: var(--user-bubble);
  color: var(--user-text);
  border-radius: 14px;
  border-bottom-right-radius: 4px;
  padding: 10px 14px;
  font-size: 15px; line-height: 1.55;
  max-width: 78%;
  white-space: pre-wrap; word-wrap: break-word;
}

/* Assistant: NO bubble, just text on white. Copilot pattern. */
.msg.assistant .bubble {
  background: transparent;
  color: var(--assistant-text);
  padding: 4px 0;
  font-size: 15.5px; line-height: 1.65;
  max-width: 100%;
  white-space: normal; word-wrap: break-word;
}
.msg.assistant .bubble ul,
.msg.assistant .bubble ol { margin: 8px 0 8px 24px; padding: 0; }
.msg.assistant .bubble li { margin: 3px 0; }
.msg.assistant .bubble strong { font-weight: 600; }

/* System: small italic note */
.msg.system .bubble {
  background: transparent; color: var(--muted);
  font-size: 14px; padding: 2px 0; font-style: italic;
}
.msg.error .bubble {
  background: #fdecec; color: #8a1c1c; border: 1px solid #f5c2c2;
  border-radius: 8px; padding: 8px 12px;
}

.typing { display: inline-flex; align-items: center; gap: 4px; padding: 4px 0; }
.typing span {
  width: 6px; height: 6px; border-radius: 50%;
  background: #9ca3af; animation: blink 1.2s infinite ease-in-out both;
}
.typing span:nth-child(2) { animation-delay: 0.15s; }
.typing span:nth-child(3) { animation-delay: 0.3s; }
@keyframes blink {
  0%, 80%, 100% { opacity: 0.3; transform: translateY(0); }
  40% { opacity: 1; transform: translateY(-2px); }
}

/* ===== Sponsored block (Copilot-style) ===== */
.sponsored-msg { justify-content: flex-start; }
.sponsored-card {
  width: 100%;
  background: var(--sponsored-bg);
  border: 1px solid var(--sponsored-border);
  border-radius: 12px;
  padding: 14px 16px;
}
.sponsored-header {
  display: flex; align-items: center; gap: 6px;
  font-size: 12px; font-weight: 500; color: #4b5563;
  margin-bottom: 8px;
}
.sponsored-source-icon { display: inline-flex; }
.sponsored-source-name { letter-spacing: 0.1px; }
.sponsored-intro {
  font-size: 14.5px; line-height: 1.55; color: var(--text);
  margin-bottom: 8px;
  min-height: 1.55em;
}
.sponsored-pill-label {
  font-size: 11px; font-weight: 600; color: var(--muted);
  letter-spacing: 0.4px; margin-bottom: 10px;
}
.sponsored-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}
.vitamin-card {
  display: flex; flex-direction: column;
  background: transparent;
  border: none; border-radius: 8px;
  padding: 0;
  text-decoration: none; color: inherit;
  cursor: pointer;
  transition: transform 0.12s ease;
}
.vitamin-card:hover { transform: translateY(-1px); }
/* Stagger reveal (used in personalized arms) */
.vitamin-card-enter { opacity: 0; transform: translateY(8px); transition: opacity 320ms ease, transform 320ms ease; }
.vitamin-card-enter.vitamin-card-enter-active { opacity: 1; transform: translateY(0); }

.vitamin-img-wrap {
  width: 100%; aspect-ratio: 1 / 1;
  border-radius: 8px; overflow: hidden;
  background: #f5f5f5; margin-bottom: 6px;
  display: flex; align-items: center; justify-content: center;
}
.vitamin-img { width: 100%; height: 100%; object-fit: cover; display: block; }
.vitamin-body { display: flex; flex-direction: column; gap: 2px; }
.vitamin-name {
  font-weight: 600; font-size: 13px; color: var(--text);
  line-height: 1.3;
  display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical;
  overflow: hidden;
}
.vitamin-price { font-size: 12px; color: var(--text-soft); margin-top: 2px; }
.vitamin-source { font-size: 11.5px; color: var(--muted); }
.vitamin-personalized-blurb {
  font-size: 12px; color: var(--text-soft);
  line-height: 1.4; margin-top: 4px;
  display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical;
  overflow: hidden;
}

/* ===== Composer ===== */
.composer {
  position: fixed; bottom: 0; left: 0; right: 0;
  background: linear-gradient(180deg, rgba(255,255,255,0) 0%, var(--bg) 30%);
  padding: 14px 18px 22px;
  justify-content: center;
}
.composer-inner {
  width: 100%; max-width: var(--max-width);
  display: flex; align-items: flex-end; gap: 8px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 6px 6px 6px 18px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
}
#input {
  flex: 1; border: none; outline: none; background: transparent;
  resize: none; font: inherit; font-size: 15px; color: var(--text);
  max-height: 160px; line-height: 1.4; padding: 8px 4px;
}
#input::placeholder { color: #9ca3af; }
#sendBtn {
  flex-shrink: 0; width: 34px; height: 34px; border-radius: 50%;
  border: none; background: var(--accent); color: #ffffff;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer; transition: background 0.12s ease;
}
#sendBtn:hover { background: var(--accent-strong); }
#sendBtn:disabled { background: #d1d5db; cursor: not-allowed; }

/* ===== Topic picker ===== */
.topic-picker {
  display: grid; grid-template-columns: 1fr 1fr; gap: 8px;
  width: 100%; max-width: 460px; margin: 4px 0 0;
}
.topic-picker.hidden { display: none; }
.topic-chip {
  display: flex; align-items: center; gap: 10px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 10px; padding: 10px 14px;
  font-family: inherit; font-size: 14px; color: var(--text);
  text-align: left; cursor: pointer;
  transition: border-color 0.12s ease, background 0.12s ease;
}
.topic-chip:hover, .topic-chip:focus-visible {
  border-color: var(--accent); background: var(--accent-soft); outline: none;
}
.topic-icon { font-size: 18px; line-height: 1; }
.topic-label { flex: 1; }

/* ===== Recall screen ===== */
.recall-grid {
  display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px;
  margin: 16px 0 22px;
}
@media (max-width: 600px) { .recall-grid { grid-template-columns: repeat(2, 1fr); } }
.recall-tile {
  position: relative; cursor: pointer;
  border: 2px solid var(--border); border-radius: 10px;
  overflow: hidden; padding: 0;
  background: var(--surface);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.recall-checkbox {
  position: absolute; top: 8px; left: 8px;
  width: 18px; height: 18px; z-index: 2; cursor: pointer;
}
.recall-tile:has(.recall-checkbox:checked) {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--accent-soft);
}
.recall-tile-frame { width: 100%; aspect-ratio: 1 / 1; background: #f5f5f5; }
.recall-tile-img { width: 100%; height: 100%; object-fit: cover; display: block; }
.recall-tile-name {
  font-size: 12.5px; padding: 6px 8px 8px; color: var(--text); font-weight: 500;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical;
  overflow: hidden; line-height: 1.3;
}

/* ===== Relevance drag-and-drop ===== */
.relevance-track-wrap { margin: 18px 0 12px; }
.relevance-track-labels {
  display: flex; justify-content: space-between;
  font-size: 13px; color: var(--text-soft); margin-bottom: 8px;
}
.relevance-track {
  position: relative;
  height: 96px;
  background: #fafafa;
  border: 1px dashed var(--border);
  border-radius: 12px;
  margin: 0 0 16px;
  touch-action: none;
}
.relevance-track-line {
  position: absolute; top: 50%; left: 14px; right: 14px;
  height: 3px; background: linear-gradient(90deg, #fca5a5 0%, #fde68a 50%, #86efac 100%);
  border-radius: 999px; transform: translateY(-50%);
}
.relevance-tray {
  display: flex; flex-wrap: wrap; gap: 12px;
  padding: 14px; background: #fff;
  border: 1px solid var(--border-soft); border-radius: 10px;
  margin-bottom: 18px; min-height: 110px;
}
.relevance-tray-empty {
  color: var(--muted); font-size: 13px; font-style: italic;
  align-self: center;
}
.relevance-token {
  position: relative;
  width: 86px;
  background: #fff; border: 1px solid var(--border);
  border-radius: 10px; padding: 8px 8px 6px;
  cursor: grab; user-select: none;
  transition: transform 0.1s ease, box-shadow 0.1s ease;
  touch-action: none;
}
.relevance-token:active,
.relevance-token.is-dragging { cursor: grabbing; box-shadow: 0 4px 14px rgba(0,0,0,0.18); transform: scale(1.04); }
.relevance-token.on-track {
  position: absolute;
  top: 50%; transform: translate(-50%, -50%);
  z-index: 2;
}
.relevance-token-img {
  width: 100%; aspect-ratio: 1/1; object-fit: cover;
  border-radius: 6px; background: #f3f4f6;
}
.relevance-token-name {
  font-size: 11px; color: var(--text); font-weight: 500;
  margin-top: 4px; line-height: 1.25;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical;
  overflow: hidden;
}

@media (max-width: 620px) {
  .sponsored-grid { grid-template-columns: repeat(2, 1fr); }
  body { font-size: 15px; }
  .topbar-right .session-tag { display: none; }
}