/* Authentic Duolingo look: white background, Duo-green 3D buttons, rounded font,
   bright HUD colors. (This app intentionally does NOT use the site's navy theme —
   it mimics Duolingo's own UI.) */
:root {
  --bg: #ffffff;
  --surface: #ffffff;
  --panel: #f7f7f7;
  --border: #e5e5e5;
  --text: #3c3c3c;
  --muted: #afafaf;
  --sub: #777777;

  --green: #58cc82;        /* Duo green */
  --green-hover: #61e786;
  --green-shadow: #58a700; /* darker green for the 3D button edge */
  --green-soft: #d7ffb8;

  --blue: #1cb0f6;         /* selection / links */
  --blue-shadow: #1899d6;
  --blue-soft: #ddf4ff;
  --blue-border: #84d8ff;

  --red: #ff4b4b;          /* hearts / wrong */
  --red-shadow: #ea2b2b;
  --red-soft: #ffdfe0;

  --gold: #ffc800;         /* XP */
  --orange: #ff9600;       /* streak */
  --purple: #ce82ff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Nunito", ui-rounded, "SF Pro Rounded", "Segoe UI", system-ui, -apple-system, sans-serif;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  max-width: 960px;
  margin: 0 auto;
  padding: 22px 20px 4px;
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand .logo { font-size: 2rem; }
.topbar h1 { font-size: 1.4rem; margin: 0; font-weight: 800; letter-spacing: -0.02em; color: var(--green); }
.tagline { color: var(--sub); margin: 2px 0 0; font-size: 0.85rem; font-weight: 600; }
.back { color: var(--blue); text-decoration: none; font-size: 0.82rem; font-weight: 700; white-space: nowrap; opacity: 0.9; }
.back:hover { opacity: 1; }

.hud { display: flex; gap: 10px; max-width: 960px; margin: 10px auto 0; padding: 0 20px; }
.hud-item {
  background: var(--surface); border: 2px solid var(--border); border-radius: 999px;
  padding: 5px 14px; font-size: 0.95rem; font-weight: 800;
}
.hud-item b { font-variant-numeric: tabular-nums; }
.hud-item.streak { color: var(--orange); }
.hud-item.xp { color: var(--gold); }
.hud-item.hearts { color: var(--red); }

/* ---- Home / lesson path ---- */
.home { max-width: 960px; margin: 18px auto 60px; padding: 0 20px; }
.unit { margin-bottom: 30px; }
.unit-head {
  display: flex; align-items: center; gap: 10px; margin-bottom: 18px;
  background: var(--green); color: #fff; border-radius: 16px; padding: 14px 18px;
  box-shadow: 0 4px 0 var(--green-shadow);
}
.unit-head .icon { font-size: 1.4rem; }
.unit-head h2 { font-size: 1.05rem; margin: 0; font-weight: 800; }
.unit-head .u-sub { color: rgba(255,255,255,0.9); font-size: 0.8rem; font-weight: 700; }
.path { display: flex; flex-direction: column; align-items: center; gap: 4px; }
.node-wrap { display: flex; flex-direction: column; align-items: center; }
.node {
  width: 74px; height: 74px; border-radius: 50%;
  border: none; cursor: pointer; font-size: 1.7rem;
  display: grid; place-items: center;
  background: #e5e5e5; color: #fff;
  box-shadow: 0 6px 0 #c8c8c8;
  transition: transform 0.08s;
}
.node:active { transform: translateY(4px); box-shadow: 0 2px 0 #c8c8c8; }
.node.done { background: var(--green); color: #fff; box-shadow: 0 6px 0 var(--green-shadow); }
.node.current { background: var(--green); color: #fff; box-shadow: 0 6px 0 var(--green-shadow); animation: bob 1.6s ease-in-out infinite; }
.node.locked { background: #e5e5e5; color: #afafaf; cursor: not-allowed; box-shadow: 0 6px 0 #c8c8c8; }
@keyframes bob { 0%,100%{ transform: translateY(0);} 50%{ transform: translateY(-5px);} }
.node-label { font-size: 0.78rem; color: var(--sub); font-weight: 700; margin: 8px 0 12px; text-align: center; max-width: 140px; }
.connector { width: 4px; height: 20px; background: var(--border); border-radius: 2px; }

/* ---- Lesson player ---- */
.lesson { max-width: 640px; margin: 20px auto; padding: 0 20px 40px; }
.lesson-top { display: flex; align-items: center; gap: 14px; margin-bottom: 24px; }
.quit { background: none; border: none; color: var(--muted); font-size: 1.4rem; font-weight: 800; cursor: pointer; padding: 0; }
.quit:hover { color: var(--sub); }
.lprogress { flex: 1; height: 16px; background: var(--border); border-radius: 999px; overflow: hidden; }
.lprogress-bar {
  height: 100%; background: var(--green); border-radius: 999px; width: 0%; transition: width 0.3s;
  box-shadow: inset 0 4px 0 rgba(255,255,255,0.3);
}
.lhearts { font-weight: 800; font-size: 1rem; color: var(--red); white-space: nowrap; }

.q-count { color: var(--muted); font-size: 0.8rem; font-weight: 800; text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 10px; }
.q-text { font-size: 1.5rem; font-weight: 800; margin: 0 0 24px; line-height: 1.35; color: var(--text); }
.options { display: grid; gap: 12px; }
.opt {
  text-align: left; padding: 16px 18px; border-radius: 16px;
  border: 2px solid var(--border); border-bottom-width: 4px; background: var(--surface);
  color: var(--text); font: inherit; font-weight: 700; font-size: 1rem; cursor: pointer;
  transition: border-color 0.12s, background 0.12s;
}
.opt:hover { background: #f7f7f7; }
.opt.selected { border-color: var(--blue-border); background: var(--blue-soft); color: #1899d6; }
.opt.correct { border-color: var(--green); background: var(--green-soft); color: var(--green-shadow); }
.opt.wrong { border-color: var(--red); background: var(--red-soft); color: var(--red-shadow); }
.opt:disabled { cursor: default; }

.feedback { margin-top: 20px; padding: 0; border-radius: 16px; font-size: 0.98rem; font-weight: 700; }
.feedback.show { padding: 16px 18px; }
.feedback.good { background: var(--green-soft); color: var(--green-shadow); }
.feedback.bad { background: var(--red-soft); color: var(--red-shadow); }
.feedback .fb-title { font-weight: 800; margin-bottom: 4px; }

.lesson-foot { margin-top: 26px; }
.btn {
  border: none; border-radius: 16px; padding: 15px 22px; font: inherit; font-weight: 800; font-size: 1rem;
  text-transform: uppercase; letter-spacing: 0.06em; cursor: pointer; width: 100%;
  transition: filter 0.12s, transform 0.06s;
}
.btn.primary { background: var(--green); color: #fff; box-shadow: 0 4px 0 var(--green-shadow); }
.btn.primary:hover { background: var(--green-hover); }
.btn.primary:active { transform: translateY(2px); box-shadow: 0 2px 0 var(--green-shadow); }
.btn.primary:disabled { background: var(--border); color: var(--muted); box-shadow: 0 4px 0 #d0d0d0; cursor: default; }

/* ---- Result ---- */
.result { max-width: 520px; margin: 40px auto; padding: 0 20px; text-align: center; }
.result h2 { font-size: 1.9rem; margin: 10px 0 6px; font-weight: 800; color: var(--green); }
.result .sub { color: var(--sub); font-weight: 600; margin-bottom: 24px; }
.result .stats { display: flex; gap: 12px; justify-content: center; margin-bottom: 28px; }
.stat { background: var(--surface); border: 2px solid var(--border); border-radius: 16px; padding: 16px 20px; min-width: 92px; }
.stat .v { font-size: 1.5rem; font-weight: 800; }
.stat .l { color: var(--muted); font-size: 0.74rem; font-weight: 800; text-transform: uppercase; letter-spacing: 0.06em; }
.stat.xp .v { color: var(--gold); }
.stat.acc .v { color: var(--green); }

.hidden { display: none !important; }

@media (max-width: 560px) {
  .q-text { font-size: 1.3rem; }
  .node { width: 66px; height: 66px; font-size: 1.5rem; }
}