:root {
  --bg-color: #ffffff;
  --text-color: #000000;
  --card-bg: #f3f3f3;
}


body {
  background: var(--bg-color);
  color: var(--text-color);
  font-family: 'Inter', sans-serif;
  margin: 0;
  padding: 0;
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main {
  flex: 1;
}

header, footer {
  background: var(--card-bg);
  padding: 1rem;
  text-align: center;
}

nav a {
  margin: 0 1rem;
  text-decoration: none;
  color: var(--text-color);
}

.container {
  padding: 1rem;
}

  .card {
    background: var(--card-bg);
    padding: 1rem;
    border-radius: 0.5rem;
    margin: 0.5rem 0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s, box-shadow 0.2s;
  }

  .card:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
    cursor: pointer;
  }

button {
  padding: 0.5rem 1rem;
  margin: 0.5rem;
  border: none;
  border-radius: 0.375rem;
  background: #2563eb;
  color: #fff;
  cursor: pointer;
  transition: transform 0.2s, background 0.2s;
}

button:hover {
  background: #abbbff;
  transform: translateY(-2px);
}

.selected-option {
  background: #dbeafe;
  color: #abc0f8;
}

  .progress {
    width: 100%;
    background: var(--card-bg);
    height: 10px;
    border-radius: 5px;
    margin-bottom: 1rem;
    overflow: hidden;
  }

  .progress-bar {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, #4f46e5, #7c3aed);
    border-radius: 5px;
    transition: width 0.3s;
  }

.flashcard {
  perspective: 1000px;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.6s;
}

.flashcard.is-flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  padding: 1rem;
  background: var(--card-bg);
  border-radius: 12px;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: box-shadow 0.3s, transform 0.3s;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.flashcard:hover .flashcard-front,
.flashcard:hover .flashcard-back {
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}