* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Arial, sans-serif;
}

body {
  background: #0f172a;
  color: #e2e8f0;
  min-height: 100vh;
}

.top-bar {
  text-align: center;
  padding: 20px;
  position: relative;
}

.home-btn {
  position: absolute;
  left: 20px;
  top: 20px;
  padding: 10px 15px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: #334155;
  color: white;
}

.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 70vh;
}

.screen {
  display: none;
  width: 100%;
  max-width: 900px;
  text-align: center;
}

.active {
  display: block;
}

/* START */
.category-grid {
  display: flex;
  justify-content: center;
  gap: 20px;
  margin-top: 30px;
}

.category-card {
  padding: 30px;
  font-size: 1.2rem;
  border-radius: 15px;
  border: none;
  cursor: pointer;
  background: #1e293b;
  color: white;
  transition: 0.3s;
}

.category-card:hover {
  transform: scale(1.05);
  background: #334155;
}

/* QUIZ */
.quiz-box {
  background: #1e293b;
  padding: 30px;
  border-radius: 15px;
}

.btn-row {
  margin-top: 20px;
}

button {
  padding: 12px 20px;
  margin: 10px;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  font-size: 1rem;
}

#trueBtn {
  background: #22c55e;
  color: white;
}

#falseBtn {
  background: #ef4444;
  color: white;
}

.next-btn {
  background: #3b82f6;
  color: white;
  margin-top: 20px;
}

.hidden {
  display: none;
}

.correct {
  color: #22c55e;
}

.wrong {
  color: #ef4444;
}