:root{
  --bg:#0b120d;
  --panel:#0f2a1a;      /* chalkboard dark */
  --panel2:#11351f;     /* chalkboard mid */
  --text:#f7fff2;       /* chalk white */
  --muted:#cfe5d2;      /* soft mint */
  --accent:#ffd166;     /* chalk yellow */
  --btn:#1a4a2c;
  --btnActive:#1f5a36;
  --good:#2ecc71;
  --bad:#ff6b6b;
}
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  background:linear-gradient(135deg, var(--bg), #0f1530 60%, #090e22);
  color:var(--text);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
}
.app{
  height:100dvh;
  display:grid;
  grid-template-columns: 1fr auto;
  grid-template-rows: auto 1fr auto;
  gap:10px;
  padding:12px;
  max-width: 700px;
  margin: 0 auto;
}
.header{
  grid-column:1 / span 2;
  display:flex;
  align-items:center;
  justify-content:space-between;
  background:var(--panel);
  border:1px solid #232a55;
  border-radius:16px;
  padding:10px 12px;
  box-shadow: 0 6px 24px rgba(0,0,0,0.25);
}
.title{
  font-weight:700;
  letter-spacing:.3px;
  font-size: 16px;
}
.actions{
  display:flex; gap:8px; align-items:center;
}
button, .btn{
  appearance:none;
  border:1px solid #2a3266;
  background:var(--btn);
  color:var(--text);
  padding:10px 12px;
  border-radius:12px;
  cursor:pointer;
}
button:hover{ background:var(--btnActive); }
#installBtn{ border-color:#3a4bd9; }
#saveToast{
  position: fixed;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  background: #18235a;
  border:1px solid #2a3a7a;
  color: var(--text);
  padding: 10px 14px;
  border-radius: 12px;
  display:none;
  box-shadow: 0 6px 24px rgba(0,0,0,0.35);
  z-index:10;
}

.main{
  grid-row: 2 / span 1;
  grid-column: 1 / span 1;
  background:var(--panel2);
  border:1px solid #232a55;
  border-radius:16px;
  padding:14px;
  display:flex;
  flex-direction:column;
  gap:12px;
  box-shadow: inset 0 0 0 1px rgba(255,255,255,0.03);
}
.display{
  flex:1;
  background: rgba(0,0,0,0.15);
  border:1px dashed #2a3266;
  border-radius:14px;
  padding:14px;
  display:flex;
  flex-direction:column;
  justify-content:center;
  gap:10px;
  user-select:none;
  touch-action: pan-y;
}
.levelTag{
  font-size:12px; color:var(--muted);
}
.sentence{
  font-size:20px; line-height:1.4; font-weight:700;
}
.translation{ font-size:16px; color:#cfd7ff; }
.notes{ font-size:13px; color:var(--muted); }

.controls{
  display:flex; gap:8px; justify-content:center; flex-wrap:wrap;
}
.controls button{ min-width:56px; }

.sidebar{
  grid-row: 2 / span 1;
  grid-column: 2 / span 1;
  display:flex;
  flex-direction:column;
  gap:8px;
}
.levels{
  display:flex;
  flex-direction:column;
  gap:8px;
}
.levels button{
  width:64px;
  padding:10px 8px;
}

.footer{
  grid-column:1 / span 2;
  display:flex;
  align-items:center;
  gap:10px;
  font-size:12px;
  color:var(--muted);
}

@media (max-width: 480px){
  .app{
    grid-template-columns: 1fr auto;
    padding:10px;
  }
  .levels button{ width:56px; padding:8px 6px; }
  .sentence{ font-size:18px; }
}

/* Classroom vibe add-ons */
body::before{
  content:"";
  position:fixed;
  inset:0;
  background:
    radial-gradient(1200px 800px at 10% -10%, rgba(255,255,255,0.05), transparent 60%),
    radial-gradient(1000px 700px at 110% 110%, rgba(255,255,255,0.04), transparent 60%),
    linear-gradient(135deg, #0d1a11, #0b120d 60%, #0a120c);
  pointer-events:none;
  z-index:-1;
}
.header{
  background: linear-gradient(180deg, #173f27, #102d1a);
  border: 1px solid rgba(255,255,255,0.08);
}
.title::before{
  content:"📚";
  margin-right:8px;
}
.display{
  position:relative;
  background:
    linear-gradient(transparent 24px, rgba(255,255,255,0.06) 25px) 0 0/100% 28px,
    rgba(0,0,0,0.12);
  border:1px solid rgba(255,255,255,0.08);
  box-shadow:
    0 12px 30px rgba(0,0,0,0.35),
    inset 0 0 0 1px rgba(255,255,255,0.02);
}
.display::before{
  /* margin hole like notebook */
  content:"";
  position:absolute;
  left:10px; top:12px; bottom:12px;
  width:6px; border-radius:6px;
  background:
    radial-gradient(circle at 50% 20px, #0000 0 3px, rgba(0,0,0,0.35) 3px 3.5px, #0000 3.6px) 0 0/100% 32px repeat-y,
    radial-gradient(circle, rgba(255,255,255,0.7), rgba(255,255,255,0.15));
  opacity:.4;
  pointer-events:none;
}
.levels button{
  background: linear-gradient(180deg, #225b37, #1b4c2e);
  border-color: rgba(255,255,255,0.15);
}
.controls button{
  background: linear-gradient(180deg, #225b37, #1b4c2e);
  border-color: rgba(255,255,255,0.15);
}
#installBtn{
  background: linear-gradient(180deg, #ffda7a, #ffc54f);
  color:#19311f;
  border-color:#caa24b;
}
.hint{ color:#e8f7ea; opacity:0.8; }
.dragging{
  transition:none !important;
}
.swipe-card{
  transition: transform .18s ease, opacity .18s ease;
  will-change: transform;
}

/* Bottom-right language visibility toggles */
.langToggles{
  position: fixed;
  right: 14px;
  bottom: 14px;
  display:flex;
  gap:8px;
  z-index: 20;
}
.langToggles button{
  background: linear-gradient(180deg, #225b37, #1b4c2e);
  border:1px solid rgba(255,255,255,0.15);
  color: var(--text);
  padding:10px 12px;
  border-radius: 12px;
  font-weight: 700;
  letter-spacing: .2px;
  cursor:pointer;
  box-shadow: 0 6px 18px rgba(0,0,0,0.28);
}
.langToggles button.active{
  outline: 2px solid var(--accent);
  filter: drop-shadow(0 6px 18px rgba(255, 209, 0, 0.25));
}
@media (max-width: 480px){
  .langToggles{
    right: 10px;
    bottom: 10px;
    gap:6px;
  }
  .langToggles button{ padding:8px 10px; }
}