/* ==========================================================================
   Sign-up and sign-in: one question at a time, large and calm, in the landing page's look.
   ========================================================================== */

:root {
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", system-ui, sans-serif;
  --bg: #f6f5f1; --paper: #fff; --field: rgba(255, 255, 255, 0.7);
  --ink: #1d1d1f; --ink-2: #4a4a50; --ink-3: #66666e; --ink-4: #a2a2a9;
  --rule: #e2e0da; --rule-strong: #cfccc4;
  --accent: #5b5bd6; --accent-ink: #4848c2; --accent-text: #4848c2;
  --accent-soft: rgba(91, 91, 214, 0.1); --accent-softer: rgba(91, 91, 214, 0.05);
  --danger: #c4372f; --good: #2f9e55;
  --shadow: 0 0 0 0.5px rgba(0, 0, 0, 0.07), 0 18px 40px -18px rgba(30, 30, 50, 0.22);
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #141416; --paper: #212125; --field: rgba(255, 255, 255, 0.04);
    --ink: #f2f2f4; --ink-2: #c0c0c7; --ink-3: #9a9aa2; --ink-4: #6a6a72;
    --rule: #2d2d32; --rule-strong: #43434a;
    --accent-text: #a9a9f7; --accent-soft: rgba(139, 139, 240, 0.16); --accent-softer: rgba(139, 139, 240, 0.07);
    --danger: #ff7b72; --good: #5cc982;
    --shadow: 0 0 0 0.5px rgba(255, 255, 255, 0.08), 0 18px 40px -18px rgba(0, 0, 0, 0.7);
    color-scheme: dark;
  }
}

*, *::before, *::after { box-sizing: border-box; }
html, body { height: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.5 var(--font); -webkit-font-smoothing: antialiased; overflow: hidden; }
a { color: inherit; }
:focus-visible { outline: 2.5px solid var(--accent); outline-offset: 3px; border-radius: 8px; }
button { font: inherit; color: inherit; }

/* ---------- shell ---------- */
.ob { position: relative; height: 100%; display: flex; flex-direction: column; }
.ob::before { content: ""; position: absolute; inset: 0; pointer-events: none; background: radial-gradient(900px 600px at 85% -10%, rgba(91, 91, 214, 0.1), transparent 60%), radial-gradient(700px 500px at -10% 110%, rgba(91, 91, 214, 0.07), transparent 60%); }
.ob-progress { position: absolute; z-index: 5; top: 0; left: 0; height: 3px; width: 0; background: var(--accent); border-radius: 0 3px 3px 0; transition: width 0.6s cubic-bezier(0.22, 1, 0.36, 1); }
.ob-top { position: relative; z-index: 2; display: flex; align-items: center; gap: 16px; padding: 18px 28px; }
.ob-brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; text-decoration: none; letter-spacing: -0.01em; min-height: 44px; }
.ob-top-link { margin-left: auto; font-size: 14px; color: var(--ink-3); }
.ob-top-link a { color: var(--ink); font-weight: 600; text-decoration: none; padding: 12px 2px; }
.ob-top-link a:hover { color: var(--accent-text); }
.ob-stage { position: relative; z-index: 1; flex: 1 1 auto; overflow-y: auto; display: grid; place-items: center; padding: 24px 28px 96px; }
.ob-screen { width: min(660px, 100%); }
.ob-nav { position: absolute; z-index: 3; right: 24px; bottom: 22px; display: flex; gap: 2px; border-radius: 12px; background: var(--paper); box-shadow: var(--shadow); overflow: hidden; }
.ob-nav button { width: 44px; height: 40px; border: 0; background: none; display: grid; place-items: center; cursor: pointer; color: var(--ink-2); }
.ob-nav button:hover:not(:disabled) { background: var(--accent-soft); color: var(--accent-text); }
.ob-nav button:disabled { color: var(--ink-4); cursor: default; }

/* ---------- question ---------- */
.ob-q-num { display: inline-flex; align-items: center; gap: 6px; margin: 0 0 14px; font-size: 14px; font-weight: 650; color: var(--accent-text); }
.ob-q-num svg { opacity: 0.8; }
.ob-q { margin: 0; font-size: clamp(26px, 4.2vw, 36px); line-height: 1.18; font-weight: 680; letter-spacing: -0.025em; text-wrap: balance; }
.ob-q em { font-style: normal; color: var(--accent-text); }
.ob-q:focus { outline: none; }
.ob-help { margin: 12px 0 0; font-size: 18px; line-height: 1.5; color: var(--ink-3); text-wrap: pretty; }
.ob-body { margin-top: 32px; }

.ob-input { width: 100%; border: 0; border-bottom: 2px solid var(--rule-strong); background: transparent; color: var(--ink); font: 500 clamp(22px, 3.4vw, 30px)/1.3 var(--font); letter-spacing: -0.01em; padding: 8px 2px 12px; outline: none; border-radius: 0; transition: border-color 0.2s; }
.ob-input::placeholder { color: var(--ink-4); }
.ob-input:focus { border-bottom-color: var(--accent); }
.ob-input:focus-visible { outline: none; }
.ob-field { position: relative; }
.ob-eye { position: absolute; right: 0; bottom: 12px; border: 0; background: none; color: var(--ink-3); font-size: 14px; font-weight: 600; padding: 10px 6px; cursor: pointer; }
.ob-eye:hover { color: var(--accent-text); }
.ob-field .ob-input { padding-right: 64px; }

.ob-strength { display: flex; align-items: center; gap: 6px; margin-top: 14px; font-size: 13px; color: var(--ink-3); }
.ob-strength i { width: 42px; height: 4px; border-radius: 2px; background: var(--rule); transition: background 0.25s; }
.ob-strength[data-level="1"] i:nth-child(-n+1) { background: var(--danger); }
.ob-strength[data-level="2"] i:nth-child(-n+2) { background: #d9902a; }
.ob-strength[data-level="3"] i:nth-child(-n+3) { background: var(--good); }
.ob-strength[data-level="4"] i:nth-child(-n+4) { background: var(--good); }
.ob-strength span { margin-left: 6px; }

.ob-choices { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 250px), 1fr)); gap: 10px; }
.ob-choice { display: flex; align-items: center; gap: 12px; min-height: 52px; padding: 10px 14px 10px 10px; border: 1.5px solid var(--rule-strong); border-radius: 12px; background: var(--field); text-align: left; font-size: 17px; cursor: pointer; transition: border-color 0.15s, background 0.15s, transform 0.15s; }
.ob-choice:hover { border-color: var(--accent); background: var(--accent-softer); }
.ob-choice:active { transform: scale(0.99); }
.ob-key { flex: 0 0 auto; display: grid; place-items: center; width: 28px; height: 28px; border-radius: 7px; border: 1.5px solid var(--rule-strong); font-size: 13px; font-weight: 700; color: var(--ink-3); background: var(--paper); transition: all 0.15s; }
.ob-choice .ob-label { flex: 1 1 auto; }
.ob-check { flex: 0 0 auto; color: var(--accent-text); opacity: 0; transform: scale(0.6); transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1); }
.ob-choice[aria-pressed="true"], .ob-choice[aria-checked="true"] { border-color: var(--accent); background: var(--accent-soft); }
.ob-choice[aria-pressed="true"] .ob-key, .ob-choice[aria-checked="true"] .ob-key { background: var(--accent); border-color: var(--accent); color: #fff; }
.ob-choice[aria-pressed="true"] .ob-check, .ob-choice[aria-checked="true"] .ob-check { opacity: 1; transform: none; }
.ob-choice.blink { animation: ob-blink 0.32s ease 2; }
@keyframes ob-blink { 50% { background: var(--accent-soft); border-color: transparent; } }

.ob-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 16px; margin-top: 30px; }
.ob-btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 48px; padding: 0 22px; border-radius: 12px; border: 0; font-size: 17px; font-weight: 650; cursor: pointer; text-decoration: none; transition: background 0.15s, transform 0.15s, box-shadow 0.15s; }
.ob-btn:active { transform: translateY(1px); }
.ob-btn:disabled { opacity: 0.55; cursor: default; }
.ob-btn-primary { background: var(--accent); color: #fff; box-shadow: 0 10px 22px -12px rgba(75, 63, 209, 0.8); }
.ob-btn-primary:hover:not(:disabled) { background: var(--accent-ink); }
.ob-btn-ghost { background: transparent; color: var(--ink-2); box-shadow: inset 0 0 0 1.5px var(--rule-strong); }
.ob-btn-ghost:hover:not(:disabled) { color: var(--ink); box-shadow: inset 0 0 0 1.5px var(--ink-3); }
.ob-btn-lg { min-height: 56px; padding: 0 30px; font-size: 18px; border-radius: 14px; }
.ob-hint { font-size: 13.5px; color: var(--ink-3); }
.ob-hint kbd { font: 600 12px var(--font); padding: 2px 6px; border-radius: 5px; background: var(--paper); box-shadow: inset 0 0 0 1px var(--rule-strong); color: var(--ink-2); }
.ob-link { border: 0; background: none; padding: 10px 2px; font-size: 15px; font-weight: 600; color: var(--accent-text); cursor: pointer; text-decoration: none; }
.ob-link:hover { text-decoration: underline; }
.ob-error { display: flex; align-items: center; gap: 8px; margin: 14px 0 0; color: var(--danger); font-size: 15px; font-weight: 550; }
.ob-error[hidden] { display: none; }
.ob-error a { color: inherit; font-weight: 700; }
.ob-shake { animation: ob-shake 0.42s cubic-bezier(0.36, 0.07, 0.19, 0.97); }
@keyframes ob-shake { 15%, 85% { transform: translateX(-2px); } 30%, 70% { transform: translateX(5px); } 45%, 55% { transform: translateX(-7px); } }

/* ---------- code ---------- */
.ob-code { display: flex; gap: 10px; }
.ob-code input { width: min(64px, 14vw); height: min(76px, 17vw); border: 1.5px solid var(--rule-strong); border-radius: 14px; background: var(--field); color: var(--ink); text-align: center; font: 700 clamp(24px, 5vw, 34px) var(--font); outline: none; caret-color: var(--accent); transition: border-color 0.15s, box-shadow 0.15s, transform 0.15s; }
.ob-code input:focus { border-color: var(--accent); box-shadow: 0 0 0 4px var(--accent-soft); }
.ob-code input.filled { border-color: var(--accent); }
.ob-code.ok input { border-color: var(--good); box-shadow: 0 0 0 4px rgba(47, 158, 85, 0.14); }
.ob-code-gap { width: 6px; }
.ob-resend { margin-top: 22px; font-size: 15px; color: var(--ink-3); display: flex; flex-wrap: wrap; gap: 4px 18px; align-items: center; }

/* ---------- invite ---------- */
.ob-invites { display: flex; flex-direction: column; gap: 6px; }
.ob-invites .ob-input { font-size: clamp(19px, 2.8vw, 24px); }
.ob-sent { display: flex; flex-direction: column; gap: 8px; margin-top: 18px; }
.ob-sent div { display: flex; align-items: center; gap: 8px; font-size: 15px; color: var(--ink-2); }
.ob-sent svg { color: var(--good); }

/* ---------- welcome + done ---------- */
.ob-hero-icon { display: block; margin: 0 0 26px; filter: drop-shadow(0 14px 28px rgba(75, 63, 209, 0.35)); }
.ob-welcome .ob-q { font-size: clamp(34px, 5.6vw, 52px); line-height: 1.06; letter-spacing: -0.035em; }
.ob-badge { display: inline-flex; align-items: center; gap: 10px; margin: 0 0 22px; padding: 6px 14px 6px 6px; border-radius: 999px; background: var(--paper); box-shadow: var(--shadow); font-size: 14.5px; color: var(--ink-2); }
.ob-badge b { color: var(--ink); }
.ob-avatar { width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; background: var(--accent); color: #fff; font-size: 11px; font-weight: 700; }
.ob-done-mark { width: 84px; height: 84px; margin: 0 0 28px; border-radius: 50%; display: grid; place-items: center; background: var(--good); color: #fff; box-shadow: 0 16px 34px -14px rgba(47, 158, 85, 0.8); }
.ob-done-mark path { stroke-dasharray: 30; stroke-dashoffset: 30; animation: ob-draw 0.55s 0.25s cubic-bezier(0.65, 0, 0.35, 1) forwards; }
@keyframes ob-draw { to { stroke-dashoffset: 0; } }
.ob-summary { display: grid; gap: 1px; margin-top: 28px; border-radius: 16px; overflow: hidden; background: var(--rule); box-shadow: var(--shadow); }
.ob-summary div { display: flex; justify-content: space-between; gap: 16px; padding: 14px 18px; background: var(--paper); font-size: 15px; }
.ob-summary dt { color: var(--ink-3); }
.ob-summary dd { margin: 0; font-weight: 600; text-align: right; }

/* ---------- sign-in card ---------- */
.ob-card { width: min(440px, 100%); background: var(--paper); border-radius: 22px; padding: 36px 34px 30px; box-shadow: var(--shadow); }
.ob-card .ob-q { font-size: 28px; }
.ob-card .ob-help { font-size: 16px; }
.ob-card .ob-body { margin-top: 24px; display: flex; flex-direction: column; gap: 16px; }
.ob-card-label { display: block; font-size: 13px; font-weight: 650; color: var(--ink-2); margin-bottom: 4px; }
.ob-card .ob-input { font-size: 19px; padding: 8px 2px 10px; }
.ob-card .ob-field .ob-eye { bottom: 8px; }
.ob-card .ob-actions { margin-top: 8px; }
.ob-card .ob-btn { width: 100%; }
.ob-card .ob-code input { width: 52px; height: 62px; font-size: 26px; border-radius: 12px; }
.ob-card .ob-code { gap: 7px; }
.ob-row-between { display: flex; justify-content: space-between; align-items: center; }
.ob-card-foot { margin: 22px 0 0; text-align: center; font-size: 14.5px; color: var(--ink-3); }
.ob-card-foot a { color: var(--ink); font-weight: 650; text-decoration: none; }
.ob-card-foot a:hover { color: var(--accent-text); }

@media (max-width: 560px) {
  .ob-top { padding: 12px 16px; }
  .ob-top-link .long { display: none; }
  .ob-stage { padding: 12px 18px 92px; place-items: start center; }
  .ob-screen { padding-top: 6vh; }
  .ob-nav { right: 16px; bottom: 16px; }
  .ob-card { padding: 28px 22px 24px; border-radius: 18px; }
  .ob-code { gap: 7px; }
}
@media (prefers-reduced-motion: reduce) {
  .ob-progress, .ob-choice, .ob-check, .ob-key { transition: none; }
  .ob-done-mark path { animation: none; stroke-dashoffset: 0; }
  .ob-shake, .ob-choice.blink { animation: none; }
}