/* Base */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', sans-serif;
}

body {
  background: linear-gradient(145deg, #1f1f1f, #2c2c2c);
  color: #f0f0f0;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.container {
  background-color: #292929;
  padding: 2rem;
  border-radius: 16px;
  box-shadow: 0 0 20px rgba(0, 255, 255, 0.1);
  width: 90%;
  max-width: 400px;
  text-align: center;
}

h1 {
  margin-bottom: 1rem;
  color: #00e6e6;
}

/* Select & Input */
select,
input[type="text"] {
  width: 100%;
  padding: 0.75rem;
  margin: 1rem 0;
  border: none;
  border-radius: 10px;
  background-color: #1a1a1a;
  color: #fff;
  font-size: 1rem;
}

button,
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  margin-top: 1rem;
  background-color: #00e6e6;
  color: #000;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  font-weight: bold;
  transition: background-color 0.3s ease;
}

button:hover,
.btn:hover {
  background-color: #00b8b8;
}

.btn.small {
  margin-top: 1rem;
  padding: 0.75rem 1.5rem;
  font-size: 0.9rem;
}

/* Flashcard Test */
.flashcard {
  background-color: #111;
  padding: 1rem;
  border-radius: 12px;
  margin: 1rem 0;
  min-height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  color: #fff;
  box-shadow: 0 0 12px rgba(0, 255, 255, 0.1);
}

/* Feedback */
#feedback {
  margin-top: 1rem;
  font-size: 1.1rem;
  font-weight: bold;
}

/* Flashcard Flip (Revision Mode) */
.flashcard-container {
  perspective: 1000px;
  margin: 2rem 0;
}

.flashcard-container .flashcard {
  width: 100%;
  height: 160px;
  transform-style: preserve-3d;
  transition: transform 0.6s;
  position: relative;
  cursor: pointer;
}

.flashcard .front,
.flashcard .back {
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 12px;
  backface-visibility: hidden;
  background-color: #111;
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  font-weight: bold;
}

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

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