:root {
  --bg: #f6f7fb;
  --card: #ffffff;
  --ink: #1b1f2a;
  --muted: #6b7280;
  --line: #e4e7ee;
  --accent: #3b5bdb;
  --accent-ink: #ffffff;
  --yes: #2f9e6f;
  --yes-bg: #e6f6ee;
  --no: #d9534f;
  --no-bg: #fdecec;
  --unseen: #d7dbe6;
  --radius: 16px;
  --nav-h: 60px;
  --shadow: 0 2px 10px rgba(20, 30, 60, 0.08);
  font-size: 17px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; background: var(--bg); color: var(--ink); }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.45;
  -webkit-text-size-adjust: 100%;
  min-height: 100dvh;
}
button { font: inherit; }
a { color: var(--accent); }

.app {
  max-width: 860px;
  margin: 0 auto;
  padding: 16px 16px calc(var(--nav-h) + env(safe-area-inset-bottom) + 16px);
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}
.loading { color: var(--muted); text-align: center; padding: 40px; }

/* ---------- nav ---------- */
.nav {
  position: fixed; left: 0; right: 0; bottom: 0;
  height: calc(var(--nav-h) + env(safe-area-inset-bottom));
  padding-bottom: env(safe-area-inset-bottom);
  display: flex; justify-content: space-around; align-items: stretch;
  background: rgba(255,255,255,0.96); backdrop-filter: blur(8px);
  border-top: 1px solid var(--line);
  z-index: 20;
}
.nav a {
  flex: 1; display: flex; flex-direction: column; align-items: center; justify-content: center;
  gap: 2px; text-decoration: none; color: var(--muted); font-size: 12px; font-weight: 600;
}
.nav a .ico { font-size: 20px; }
.nav a.active { color: var(--accent); }
body.studying .nav { display: none; }
body.studying .app { padding-bottom: 16px; }

@media (min-width: 760px) {
  .nav { top: 0; bottom: auto; height: 56px; padding-bottom: 0; border-top: 0; border-bottom: 1px solid var(--line);
         justify-content: center; gap: 12px; }
  .nav a { flex: 0 0 auto; flex-direction: row; gap: 8px; padding: 0 18px; font-size: 15px; }
  .nav a .ico { font-size: 18px; }
  .app { padding-top: 76px; padding-bottom: 32px; }
  body.studying .app { padding-top: 16px; }
}

/* ---------- generic ---------- */
h1 { font-size: 1.5rem; margin: 6px 0 4px; }
h2 { font-size: 1.1rem; margin: 22px 0 8px; }
.sub { color: var(--muted); font-size: 0.92rem; margin: 0 0 10px; }
.panel { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 16px; margin-bottom: 14px; }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.spacer { flex: 1; }
.btn {
  appearance: none; border: 1px solid var(--line); background: #fff; color: var(--ink);
  border-radius: 12px; padding: 10px 16px; cursor: pointer; font-weight: 600;
  transition: transform 0.05s ease, background 0.15s ease;
  -webkit-tap-highlight-color: transparent;
}
.btn:active { transform: scale(0.98); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.big { padding: 16px 20px; font-size: 1.1rem; border-radius: 14px; width: 100%; }
.btn.yes { background: var(--yes); border-color: var(--yes); color: #fff; }
.btn.no { background: var(--no); border-color: var(--no); color: #fff; }
.btn.ghost { background: transparent; border-color: transparent; color: var(--accent); }
.btn.small { padding: 6px 10px; font-size: 0.85rem; border-radius: 10px; }
.btn.danger { color: var(--no); border-color: var(--no-bg); background: var(--no-bg); }
.btn[disabled] { opacity: 0.5; cursor: default; }
.link { background: none; border: 0; color: var(--accent); cursor: pointer; padding: 0; font-weight: 600; }

.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  border: 1px solid var(--line); background: #fff; border-radius: 999px; padding: 7px 12px; cursor: pointer;
  font-size: 0.9rem; font-weight: 600; color: var(--muted); display: inline-flex; gap: 6px; align-items: center;
}
.chip.on { background: var(--accent); color: #fff; border-color: var(--accent); }
.chip .cnt { font-weight: 400; opacity: 0.85; }

.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; background: #fff; flex-wrap: wrap; }
.seg button { border: 0; background: transparent; padding: 9px 14px; cursor: pointer; font-weight: 600; color: var(--muted); }
.seg button.on { background: var(--accent); color: #fff; }
.field { margin: 12px 0; }
.field label.lbl { display: block; font-size: 0.85rem; font-weight: 700; color: var(--muted); text-transform: uppercase; letter-spacing: 0.04em; margin-bottom: 6px; }
.hint { font-size: 0.85rem; color: var(--muted); margin-top: 6px; }

.bar { height: 10px; background: var(--unseen); border-radius: 999px; overflow: hidden; display: flex; }
.bar .y { background: var(--yes); height: 100%; }
.bar .n { background: var(--no); height: 100%; }
.bar.tall { height: 14px; }
.legend { display: flex; gap: 14px; font-size: 0.82rem; color: var(--muted); margin-top: 6px; flex-wrap: wrap; }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: 5px; vertical-align: -1px; }
.legend .ly i { background: var(--yes); } .legend .ln i { background: var(--no); } .legend .lu i { background: var(--unseen); }

.stat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.stat { background: var(--card); border-radius: 12px; padding: 12px; box-shadow: var(--shadow); text-align: center; }
.stat b { display: block; font-size: 1.5rem; }
.stat span { font-size: 0.8rem; color: var(--muted); }
.stat.y b { color: var(--yes); } .stat.n b { color: var(--no); }

.list { list-style: none; margin: 0; padding: 0; }
.list li { border-top: 1px solid var(--line); padding: 10px 0; }
.list li:first-child { border-top: 0; }
.sec-row { display: flex; align-items: center; gap: 10px; }
.sec-row .name { flex: 1; font-weight: 600; }
.sec-row .pct { color: var(--muted); font-size: 0.9rem; min-width: 3.5em; text-align: right; }
.dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; background: var(--unseen); flex: none; }
.dot.yes { background: var(--yes); } .dot.no { background: var(--no); }

table.hist { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
table.hist th, table.hist td { text-align: left; padding: 6px 4px; border-top: 1px solid var(--line); }
table.hist th { color: var(--muted); font-weight: 600; border-top: 0; font-size: 0.8rem; }

input[type=search], textarea {
  width: 100%; font: inherit; padding: 10px 12px; border: 1px solid var(--line); border-radius: 12px; background: #fff; color: var(--ink);
}
textarea { min-height: 90px; resize: vertical; font-family: ui-monospace, Menlo, monospace; font-size: 0.8rem; }

/* ---------- browse ---------- */
.b-card { border-top: 1px solid var(--line); }
.b-card summary { list-style: none; cursor: pointer; padding: 10px 0; display: flex; gap: 10px; align-items: center; }
.b-card summary::-webkit-details-marker { display: none; }
.b-card summary .p { flex: 1; font-weight: 600; }
.b-card .ans { padding: 0 0 14px 20px; }
.b-card .tag { font-size: 0.75rem; background: var(--bg); border-radius: 6px; padding: 2px 6px; color: var(--muted); }

/* ---------- study ---------- */
.study { display: flex; flex-direction: column; flex: 1; min-height: 0; }
.study-top { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.study-top .prog { flex: 1; }
.study-top .prog .txt { font-size: 0.85rem; color: var(--muted); display: flex; justify-content: space-between; margin-bottom: 4px; }
.study-top .prog .bar { height: 6px; }
.study-top .prog .bar .p { background: var(--accent); height: 100%; transition: width 0.2s ease; }

.card {
  background: var(--card); border-radius: 20px; box-shadow: var(--shadow);
  flex: 1; min-height: 0; display: flex; flex-direction: column;
  cursor: pointer; position: relative; overflow: hidden;
  transition: transform 0.16s ease, opacity 0.16s ease;
  -webkit-tap-highlight-color: transparent;
  touch-action: pan-y;
}
.card.flipping { transform: rotateY(90deg); opacity: 0.6; }
.card .kicker { font-size: 0.75rem; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); padding: 16px 20px 0; display: flex; justify-content: space-between; }
.card .front { flex: 1; display: flex; align-items: center; justify-content: center; text-align: center; padding: 24px; overflow: auto; }
.card .front .prompt { font-size: clamp(1.25rem, 3.4vw, 1.9rem); font-weight: 700; line-height: 1.3; }
.card .back { flex: 1; min-height: 0; display: flex; flex-direction: column; }
.card .back .q { padding: 10px 20px 8px; font-weight: 700; border-bottom: 1px solid var(--line); font-size: 1rem; }
.card .back .a { flex: 1; overflow: auto; padding: 14px 20px 20px; -webkit-overflow-scrolling: touch; font-size: 1.02rem; overscroll-behavior: contain; }
.card .tap-hint { text-align: center; color: var(--muted); font-size: 0.85rem; padding: 0 0 14px; }
.card.dragging { transition: none; }

/* answer content */
.a p { margin: 0 0 0.6em; }
.a p:last-child { margin-bottom: 0; }
.a ul, .a ol { margin: 0.2em 0 0.7em; padding-left: 1.4em; }
.a ul.l1, .a ol.l1 { padding-left: 2.6em; margin-top: -0.4em; }
.a ul.l2, .a ol.l2 { padding-left: 3.8em; margin-top: -0.4em; }
.a ul.l3, .a ol.l3 { padding-left: 5em; margin-top: -0.4em; }
.a li { margin: 0.15em 0; }
.a table.inner { border-collapse: collapse; margin: 0.5em 0; font-size: 0.95em; }
.a table.inner td { border: 1px solid var(--line); padding: 4px 8px; vertical-align: top; }
.a b { font-weight: 700; }

.actions { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 12px; }
.actions .btn { padding: 16px 12px; font-size: 1.05rem; border-radius: 14px; }
.actions .btn.single { grid-column: 1 / -1; }
.actions .btn .k { display: block; font-size: 0.72rem; opacity: 0.75; font-weight: 500; margin-top: 2px; }
.under { display: flex; justify-content: space-between; align-items: center; margin-top: 8px; font-size: 0.85rem; color: var(--muted); }
@media (hover: none) { .kbd-only { display: none; } }

/* ---------- summary ---------- */
.summary { text-align: center; padding: 20px 0; }
.summary .big { font-size: 3rem; font-weight: 800; }
.summary .pile { text-align: left; margin-top: 10px; }
.summary .pile li { display: flex; gap: 8px; align-items: center; }

.toast {
  position: fixed; left: 50%; bottom: calc(var(--nav-h) + env(safe-area-inset-bottom) + 14px); transform: translateX(-50%) translateY(20px);
  background: var(--ink); color: #fff; padding: 10px 16px; border-radius: 12px; font-size: 0.9rem;
  opacity: 0; pointer-events: none; transition: opacity 0.2s ease, transform 0.2s ease; z-index: 30; max-width: 90vw;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
@media (min-width: 760px) { .toast { bottom: 24px; } }

.empty { color: var(--muted); text-align: center; padding: 30px 10px; }
.kbd { font-family: ui-monospace, Menlo, monospace; background: var(--bg); border: 1px solid var(--line); border-radius: 6px; padding: 1px 6px; font-size: 0.8em; }

/* ---------- content: images, highlights ---------- */
.a img, .front img, .q img, .b-card summary img {
  max-width: 100%; height: auto; display: block; border-radius: 8px; margin: 6px auto; cursor: zoom-in;
}
.front img { max-height: 55vh; object-fit: contain; }
.front .prompt img { margin: 0 auto; }
.card.img-prompt .front .prompt { width: 100%; }
.q img { max-height: 24vh; object-fit: contain; margin: 4px auto; }
.a img { max-height: 60vh; object-fit: contain; }
.b-card summary img { display: inline-block; max-height: 56px; width: auto; margin: 0 6px 0 0; vertical-align: middle; border-radius: 4px; }
.a mark, .q mark, .front mark, .b-card mark { padding: 0 2px; border-radius: 3px; color: inherit; }
mark.hit { background: #fff3a8; }
.a s { opacity: 0.7; }

.lightbox {
  position: fixed; inset: 0; background: rgba(15, 18, 28, 0.92); z-index: 50;
  display: flex; flex-direction: column; align-items: center; justify-content: center; cursor: zoom-out; padding: 16px;
}
.lightbox img { max-width: 100%; max-height: 90vh; object-fit: contain; border-radius: 6px; background: #fff; }
.lightbox .lb-hint { color: #cbd0dc; font-size: 0.85rem; margin-top: 10px; }

/* segmented controls fill the row on narrow screens */
.seg { display: flex; }
.seg button { flex: 1 1 auto; }

.front .prompt p, .b-card summary .p p, .q p { margin: 0; }
.b-card summary .p ul, .b-card summary .p ol, .front .prompt ul, .front .prompt ol, .q ul, .q ol { margin: 0; padding-left: 1.2em; text-align: left; }
.front .prompt ul.l0, .front .prompt ol.l0 { display: inline-block; }
.chip { text-align: left; }

/* ---------- cheer-up easter egg (teal, bubbly) ---------- */
:root {
  --teal: #5ec8c0; --teal-deep: #1f7a74; --teal-soft: #e6faf8; --teal-line: #9fe0da;
  --bubbly: ui-rounded, "SF Pro Rounded", "Nunito", "Quicksand", "Varela Round", "Arial Rounded MT Bold", "Trebuchet MS", system-ui, sans-serif;
}
.cheer-row { text-align: center; margin: 10px 0 2px; }
.cheer-pill {
  font-family: var(--bubbly); font-weight: 700; font-size: 0.88rem; color: var(--teal-deep);
  background: var(--teal-soft); border: 1.5px dashed var(--teal-line); border-radius: 999px; padding: 7px 14px;
  cursor: pointer; transition: transform 0.15s ease, background 0.15s ease; -webkit-tap-highlight-color: transparent;
}
.cheer-pill:hover { background: #d4f5f1; transform: translateY(-1px) scale(1.02); }
.cheer-nudge { display: inline-flex; align-items: center; gap: 4px; animation: cheer-in 0.5s cubic-bezier(.2,1.4,.4,1); }
.cheer-nudge .cheer-pill { font-size: 0.8rem; padding: 5px 11px; }
.cheer-x { border: 0; background: transparent; color: var(--muted); font-size: 1.1rem; line-height: 1; cursor: pointer; padding: 2px 6px; }

.cheer-overlay {
  position: fixed; inset: 0; z-index: 60; display: flex; align-items: center; justify-content: center; padding: 18px;
  background: rgba(94, 200, 192, 0.32); backdrop-filter: blur(7px); -webkit-backdrop-filter: blur(7px);
  animation: cheer-fade 0.25s ease; overflow: hidden;
}
.cheer-overlay.closing { animation: cheer-fade 0.22s ease reverse forwards; }
.cheer-card {
  position: relative; background: #fff; border-radius: 34px; padding: 18px 18px 16px; max-width: 440px; width: 100%;
  box-shadow: 0 20px 50px rgba(31, 122, 116, 0.35), 0 0 0 6px rgba(255,255,255,0.55);
  animation: cheer-pop 0.6s cubic-bezier(.2,1.5,.4,1); text-align: center; font-family: var(--bubbly);
  max-height: calc(100dvh - 36px); display: flex; flex-direction: column;
}
.cheer-frame {
  position: relative; margin: 0 auto; border-radius: 26px; background: linear-gradient(135deg, #bff0ea, #e6faf8);
  padding: 9px; box-shadow: 0 10px 26px rgba(31,122,116,0.28), inset 0 0 0 3px #fff; transform: rotate(-2deg);
  transition: transform 0.4s cubic-bezier(.2,1.4,.4,1); min-height: 160px; min-width: 200px; display: flex; align-items: center; justify-content: center;
  flex: 0 1 auto; overflow: hidden;
}
.cheer-frame.ready { transform: rotate(-1.5deg); }
.cheer-frame img { display: block; max-width: 100%; max-height: min(52vh, 480px); width: auto; border-radius: 18px; opacity: 0; transition: opacity 0.35s ease; }
.cheer-frame.ready img { opacity: 1; }
.cheer-frame.broken img { display: none; }
.cheer-spinner { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; font-size: 34px; animation: cheer-beat 1s ease-in-out infinite; }
.cheer-frame.ready .cheer-spinner { display: none; }
.cheer-msg { font-size: 1.22rem; font-weight: 800; color: var(--teal-deep); line-height: 1.35; margin: 16px 6px 4px; letter-spacing: 0.01em; }
.cheer-actions { display: flex; gap: 10px; justify-content: center; margin-top: 12px; flex-wrap: wrap; }
.cheer-btn {
  font-family: var(--bubbly); font-weight: 800; border-radius: 999px; padding: 11px 18px; border: 2px solid var(--teal-line);
  background: var(--teal-soft); color: var(--teal-deep); cursor: pointer; transition: transform 0.12s ease; -webkit-tap-highlight-color: transparent;
}
.cheer-btn.primary { background: linear-gradient(135deg, #6fd3cb, #3fb8ae); color: #fff; border-color: transparent; box-shadow: 0 6px 16px rgba(63,184,174,0.4); }
.cheer-btn:active { transform: scale(0.96); }
.cheer-hearts { position: absolute; inset: 0; pointer-events: none; overflow: hidden; }
.cheer-heart { position: absolute; bottom: -40px; animation: cheer-float 5.5s linear infinite; opacity: 0; filter: drop-shadow(0 2px 4px rgba(31,122,116,0.3)); }

@keyframes cheer-pop { 0% { transform: scale(0.5) rotate(-6deg); opacity: 0; } 60% { transform: scale(1.06) rotate(1.5deg); opacity: 1; } 100% { transform: scale(1) rotate(0); } }
@keyframes cheer-fade { from { opacity: 0; } to { opacity: 1; } }
@keyframes cheer-in { from { transform: translateY(8px) scale(0.9); opacity: 0; } to { transform: none; opacity: 1; } }
@keyframes cheer-beat { 0%, 100% { transform: scale(1); } 50% { transform: scale(1.25); } }
@keyframes cheer-float { 0% { transform: translateY(0) rotate(0); opacity: 0; } 10% { opacity: 0.9; } 90% { opacity: 0.6; } 100% { transform: translateY(-105vh) rotate(25deg); opacity: 0; } }
@media (prefers-reduced-motion: reduce) { .cheer-card, .cheer-heart, .cheer-nudge { animation: none; } }

/* ---------- unit groups ---------- */
.grp { margin: 6px 0 10px; }
.grp-name {
  display: block; background: none; border: 0; padding: 0; margin: 0 0 6px; cursor: pointer; text-align: left;
  font-size: 0.75rem; font-weight: 800; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent);
}
.grp-name:hover { text-decoration: underline; }
.list li.grp-head { font-size: 0.72rem; font-weight: 800; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); padding: 16px 0 4px; border-top: 0; }
.list li.grp-head + li { border-top: 0; }
.grp-inline { color: var(--muted); font-weight: 500; }