:root {
  --bg: #f4f6fb;
  --card: #fff;
  --text: #111827;
  --muted: #6b7280;
  --primary: #1d4ed8;
  --primary-text: #fff;
  --good: #15803d;
  --bad: #b91c1c;
  --border: #e5e7eb;
  --radius: 14px;
  /* Fonts with full Greek coverage (incl. τόνος) on iOS, Android and desktops. */
  font-family:
    system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", "Helvetica Neue", Arial,
    sans-serif;
  color: var(--text);
  background: var(--bg);
}

* { box-sizing: border-box; }
body { margin: 0; min-height: 100vh; }
a { color: var(--primary); }
h1 { font-size: 1.4rem; margin: 0.5rem 0 1rem; overflow-wrap: anywhere; }
h2 { font-size: 1.1rem; margin: 0 0 0.5rem; }

.topbar { background: var(--primary); padding: 0.75rem 1rem; }
.brand { color: #fff; text-decoration: none; font-weight: 700; }
.container { max-width: 640px; margin: 0 auto; padding: 1rem 1rem 7rem; }
.muted { color: var(--muted); }
.small { font-size: 0.9rem; }
.error { color: var(--bad); }
.back { display: inline-block; margin-bottom: 0.5rem; text-decoration: none; }

.card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 1rem;
  margin-bottom: 1rem;
  box-shadow: 0 1px 3px rgb(0 0 0 / 0.06);
}

.btn {
  display: inline-block;
  width: 100%;
  border: 0;
  border-radius: var(--radius);
  padding: 0.9rem 1rem;
  font-size: 1.05rem;
  font-weight: 600;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
  background: var(--primary);
  color: var(--primary-text);
  font-family: inherit;
}
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn.big { padding: 1.1rem; font-size: 1.15rem; }
.btn.secondary { background: #e0e7ff; color: var(--primary); }
.btn.danger { background: #fee2e2; color: var(--bad); }
.btn.good { background: var(--good); }
.btn.bad { background: var(--bad); }
.btn + .btn { margin-top: 0.6rem; }

.vocab { text-align: center; }
.vocab .number { font-size: 3rem; font-weight: 800; line-height: 1.1; color: var(--primary); }

.steps { padding-left: 1.3rem; line-height: 1.6; }

.modules { list-style: none; padding: 0; margin: 0; }
.modules a { display: block; color: inherit; text-decoration: none; }
.progress { height: 8px; border-radius: 4px; background: var(--border); overflow: hidden; margin: 0.5rem 0 0.3rem; }
.progress > div { height: 100%; background: var(--good); }

label { display: block; font-weight: 600; margin: 0.8rem 0 0.3rem; }
input[type="text"], textarea {
  width: 100%;
  font: inherit;
  font-size: 1rem;
  padding: 0.7rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #fff;
}
textarea { min-height: 10rem; resize: vertical; }

table { width: 100%; border-collapse: collapse; }
td { padding: 0.45rem 0.25rem; border-bottom: 1px solid var(--border); vertical-align: top; overflow-wrap: anywhere; }
td.greek { font-weight: 600; }
td.arrow { color: var(--muted); width: 1.5rem; text-align: center; }
.skipped td { color: var(--muted); }
.tag { display: inline-block; font-size: 0.75rem; padding: 0.1rem 0.5rem; border-radius: 999px; white-space: nowrap; }
.tag.new { background: #e0e7ff; color: var(--primary); }
.tag.learning { background: #fef3c7; color: #92400e; }
.tag.known { background: #dcfce7; color: var(--good); }
.tag.skip { background: #f3f4f6; color: var(--muted); }

.study-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 1rem; }
.flashcard { text-align: center; padding: 2.5rem 1rem; min-height: 14rem; display: flex; flex-direction: column; justify-content: center; gap: 1rem; }
.flashcard .word { font-size: 2.2rem; font-weight: 700; overflow-wrap: anywhere; }
.flashcard .translation { font-size: 1.4rem; color: var(--muted); overflow-wrap: anywhere; }
.speak { background: none; border: 1px solid var(--border); border-radius: 999px; font-size: 1.4rem; padding: 0.3rem 0.9rem; cursor: pointer; align-self: center; }

.thumb-bar {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  padding: 0.75rem 1rem calc(0.75rem + env(safe-area-inset-bottom));
  background: rgb(244 246 251 / 0.95);
  border-top: 1px solid var(--border);
}
.thumb-bar .inner { max-width: 640px; margin: 0 auto; display: flex; gap: 0.75rem; }
.thumb-bar .btn { margin: 0; padding: 1.2rem 0.5rem; font-size: 1.15rem; }