:root {
  --bg: var(--tg-theme-bg-color, #ffffff);
  --text: var(--tg-theme-text-color, #1c1c1e);
  --hint: var(--tg-theme-hint-color, #8e8e93);
  --button: var(--tg-theme-button-color, #2ea043);
  --button-text: var(--tg-theme-button-text-color, #ffffff);
  --secondary-bg: var(--tg-theme-secondary-bg-color, #f2f2f7);
  --accent: #2ea043;
  --danger: #e5484d;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  padding: 16px;
  padding-bottom: 90px;
}

h1 { font-size: 20px; margin: 4px 0 16px; }

.tabs {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  display: flex;
  background: var(--secondary-bg);
  border-top: 1px solid rgba(0,0,0,0.08);
}

.tabs button {
  flex: 1;
  padding: 14px 0;
  background: none;
  border: none;
  font-size: 14px;
  color: var(--hint);
}

.tabs button.active { color: var(--accent); font-weight: 600; }

.card {
  background: var(--secondary-bg);
  border-radius: 16px;
  padding: 20px;
  margin-bottom: 16px;
}

.expression {
  font-size: 34px;
  text-align: center;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  margin: 24px 0;
}

.frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  line-height: 1.15;
}

.frac .num, .frac .den { padding: 0 4px; }
.frac .num { border-bottom: 2px solid var(--text); }

input#answer {
  width: 100%;
  font-size: 22px;
  text-align: center;
  padding: 12px;
  border-radius: 12px;
  border: 2px solid var(--hint);
  background: var(--bg);
  color: var(--text);
}

input#answer.wrong { border-color: var(--danger); animation: shake 0.3s; }
input#answer.correct { border-color: var(--accent); }

button.primary {
  width: 100%;
  margin-top: 14px;
  padding: 14px;
  border: none;
  border-radius: 12px;
  background: var(--button);
  color: var(--button-text);
  font-size: 17px;
  font-weight: 600;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-6px); }
  75% { transform: translateX(6px); }
}

.feedback { text-align: center; margin-top: 10px; min-height: 22px; font-size: 15px; }
.feedback.wrong { color: var(--danger); }
.feedback.correct { color: var(--accent); }

.progress-bar-track {
  background: rgba(0,0,0,0.08);
  border-radius: 8px;
  height: 10px;
  overflow: hidden;
}
.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  transition: width 0.4s ease;
}

.week-row { display: flex; justify-content: space-between; align-items: center; margin-bottom: 8px; }
.badge-improved {
  background: var(--accent);
  color: #fff;
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 10px;
  margin-left: 8px;
}

table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { text-align: left; padding: 8px 6px; border-bottom: 1px solid rgba(0,0,0,0.08); }

.student-row { cursor: pointer; }
.student-row:active { background: rgba(0,0,0,0.04); }

input.inline-edit {
  width: 100%;
  border: 1px solid var(--hint);
  border-radius: 6px;
  padding: 4px 6px;
  font-size: 14px;
  background: var(--bg);
  color: var(--text);
}

#confetti-canvas {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 999;
}

.hidden { display: none !important; }
.muted { color: var(--hint); font-size: 13px; }