:root {
  --bg: #10243a;
  --bg-2: #17324e;
  --paper: #f7f4ee;
  --ink: #1c1915;
  --muted: #5f5a52;
  --line: #e3ddd2;
  --teal: #0e7c73;
  --teal-deep: #0a534d;
  --ok: #1c7c43;
  --ok-bg: #e5f6eb;
  --bad: #b42318;
  --bad-bg: #fdeceb;
  --chip: #e7f3f2;
  color-scheme: dark;
}

* { box-sizing: border-box; }

[hidden] { display: none !important; }

html, body { height: 100%; }

body {
  margin: 0;
  font-family: "Segoe UI", "Avenir Next", sans-serif;
  background:
    radial-gradient(1200px 500px at 10% -10%, #1d4d73 0%, transparent 55%),
    var(--bg);
  color: #f4efe6;
}

#study {
  height: 100dvh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.login {
  min-height: 100dvh;
  display: grid;
  place-items: center;
  padding: 1.5rem;
}
.login form {
  width: min(380px, 100%);
  display: grid;
  gap: 0.75rem;
  background: rgba(8, 20, 34, 0.55);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 22px;
  padding: 1.4rem;
}
.login h1 { font-size: 2rem; }
.login-lead { margin: 0; color: #d5e4ea; }
.login .note { margin: 0; }
.error { margin: 0; color: #ffb4ab; min-height: 1.2em; }
.login button { justify-self: start; }

button, input { font: inherit; }

button {
  border: 0;
  border-radius: 999px;
  padding: 0.7rem 1.1rem;
  background: #23405f;
  color: #f7f4ee;
  cursor: pointer;
}

button:hover { filter: brightness(1.08); }
button:disabled { opacity: 0.45; cursor: default; }
button.primary { background: var(--teal); color: white; }
button.ghost { background: transparent; color: inherit; border: 1px solid currentColor; }
button[aria-pressed="true"] { background: var(--teal); color: white; }

.top, .panel, main {
  width: min(880px, calc(100% - 1.5rem));
  margin-inline: auto;
}

.top {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: end;
  padding: 0.8rem 0 0.4rem;
  flex: 0 0 auto;
}
.top-side { display: flex; gap: 0.7rem; align-items: center; }

.eyebrow {
  margin: 0;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.72rem;
  color: #b7c7d6;
}

h1 { margin: 0.15rem 0 0; font-size: 1.8rem; font-weight: 650; }

.stats { margin: 0; color: #d5e4ea; text-align: right; }

.panel {
  margin-top: 0.4rem;
  padding: 0.75rem 0.9rem;
  border-radius: 18px;
  background: rgba(8, 20, 34, 0.45);
  border: 1px solid rgba(255, 255, 255, 0.08);
  flex: 0 1 auto;
  max-height: 30dvh;
  overflow: auto;
}
.panel summary {
  cursor: pointer;
  font-weight: 650;
  margin-bottom: 0.7rem;
}

.group { margin-bottom: 0.7rem; }
.group h2 {
  margin: 0 0 0.35rem;
  font-size: 0.75rem;
  font-weight: 650;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: #b7c7d6;
}

.chips { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.chips button { padding: 0.45rem 0.75rem; background: #1c3652; }
.chips button small { display: block; font-size: 0.72rem; opacity: 0.8; }

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 0.9rem;
  align-items: center;
  margin-top: 0.4rem;
}

.segment { display: flex; flex-wrap: wrap; gap: 0.3rem; }
.segment button { background: #1c3652; }

.switch {
  display: flex;
  gap: 0.4rem;
  align-items: center;
  color: #e7eef3;
}

.position {
  margin: 1rem 0 0.4rem;
  color: #c5d4e0;
}

.card {
  background: var(--paper);
  color: var(--ink);
  border-radius: 22px;
  padding: 1rem 1.1rem 0.9rem;
  box-shadow: 0 18px 50px rgba(0, 0, 0, 0.22);
}

.meta {
  display: flex;
  justify-content: space-between;
  gap: 0.8rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.badge {
  border-radius: 999px;
  padding: 0.15rem 0.6rem;
  background: var(--line);
}
.badge.known { background: var(--ok-bg); color: var(--ok); }
.badge.unknown { background: #fff1e8; color: #c2410c; }

.prompt {
  font-size: 1.25rem;
  line-height: 1.45;
  margin: 0.8rem 0;
}

.figure {
  margin: 0 0 0.8rem;
}
.figure img, .option img {
  max-width: 100%;
  height: auto;
  border-radius: 12px;
  background: white;
  cursor: zoom-in;
}
.figure img { max-height: 140px; object-fit: contain; }

.options { display: grid; gap: 0.55rem; }
.option {
  width: 100%;
  text-align: left;
  border-radius: 14px;
  padding: 0.75rem 0.85rem;
  background: white;
  color: var(--ink);
  border: 2px solid var(--line);
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.7rem;
  align-items: start;
}
.option .letter {
  width: 1.7rem;
  height: 1.7rem;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: var(--chip);
  color: var(--teal-deep);
  font-weight: 700;
}
.option.picked { border-color: #7aa7b5; }
.option.correct { border-color: var(--ok); background: var(--ok-bg); }
.option.wrong { border-color: var(--bad); background: var(--bad-bg); }
.option img { max-height: 72px; width: auto; object-fit: contain; grid-column: 2; }

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-top: 0.9rem;
}
.actions button { color: var(--ink); background: #efeae2; }
.actions button.primary { color: white; background: var(--teal); }
.actions button.on-known { background: var(--ok); color: white; }
.actions button.on-unknown { background: #c2410c; color: white; }

main {
  flex: 1 1 auto;
  min-height: 0;
  display: flex;
  flex-direction: column;
  margin-bottom: 0.5rem;
}
.position { flex: 0 0 auto; margin: 0.45rem 0; }
.card {
  flex: 1 1 auto;
  min-height: 0;
  overflow: auto;
}
.nav {
  display: flex;
  justify-content: space-between;
  gap: 0.6rem;
  flex: 0 0 auto;
  margin: 0.55rem 0 0;
}
.nav button { min-width: 8rem; }

.more {
  margin-bottom: 2rem;
  color: #d5e0e8;
}
.more summary { cursor: pointer; }
.more-body { display: grid; gap: 0.8rem; margin-top: 0.7rem; }
.more-body p { margin: 0; }
#sync-form, .backup {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  align-items: end;
}
#sync-form label, .file { display: grid; gap: 0.25rem; font-size: 0.9rem; }
input[type="text"], input[type="password"], input:not([type]) {
  background: #0d1c2e;
  color: white;
  border: 1px solid #34506c;
  border-radius: 10px;
  padding: 0.55rem 0.7rem;
}
.note { font-size: 0.85rem; color: #b7c6d3; }
#sync-status { align-self: center; }

#lightbox {
  border: 0;
  padding: 0.6rem;
  background: #0d1c2e;
  color: white;
  max-width: min(960px, 96vw);
}
#lightbox img { max-width: 100%; height: auto; display: block; }
#lightbox::backdrop { background: rgba(0, 0, 0, 0.72); }

.empty { color: var(--muted); }

@media (max-width: 700px) {
  .top { flex-direction: column; align-items: start; }
  .stats { text-align: left; }
  .prompt { font-size: 1.12rem; }
  .nav button { flex: 1; }
}