:root {
  --bg-color: #1a1a1a;
  --text-color: #ffffff;
  --primary-color: #4a9eff;
  --primary-gradient: linear-gradient(90deg, #4a9eff 0%, #2461b5 100%);
  --secondary-color: #2d2d2d;
  --accent-color: #ff4a4a;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Segoe UI', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
}

header {
  text-align: center;
  margin-bottom: 3rem;
}

h1 {
  font-size: 2.5rem;
  margin-bottom: 1.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  display: inline-block;
}

nav {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

button {
  background-color: var(--secondary-color);
  color: var(--text-color);
  border: none;
  padding: 0.8rem 1.5rem;
  border-radius: 5px;
  cursor: pointer;
  transition: all 0.3s;
}

button:hover {
  background: var(--primary-gradient);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

button:disabled:hover {
  background-color: var(--secondary-color);
}

.screen {
  display: none;
  text-align: center;
}

.screen.active {
  display: block;
}

.card {
  perspective: 1000px;
  width: 400px;
  height: 250px;
  margin: 2rem auto;
  cursor: pointer;
}

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

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

.card-front, .card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  background: var(--secondary-color);
  border-radius: 10px;
  border: 2px solid transparent;
  background-clip: padding-box;
  transition: opacity 0.25s ease;
}

.card-front {
  background: linear-gradient(var(--secondary-color), var(--secondary-color)) padding-box,
              var(--primary-gradient) border-box;
}

.card-back {
  transform: rotateY(180deg);
  background: linear-gradient(var(--secondary-color), var(--secondary-color)) padding-box,
              var(--primary-gradient) border-box;
}

.controls {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin: 2rem 0;
}

.progress-container {
  margin-top: 2rem;
}

.progress {
  width: 100%;
  height: 10px;
  background-color: var(--secondary-color);
  border-radius: 5px;
}

.progress-stats {
  text-align: right;
  margin-top: 0.5rem;
  color: var(--text-color);
  opacity: 0.8;
  font-size: 0.9rem;
}

#progress-bar {
  height: 100%;
  background: var(--primary-gradient);
  border-radius: 5px;
  transition: width 0.3s;
}

#stats-content {
  margin-top: 2rem;
}

.list-selector {
  margin: 2rem 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
}

.list-selector p {
  margin: 0;
}

.selectors-container {
  display: flex;
  gap: 1rem;
  align-items: center;
}

.selectors-container select {
  min-width: 200px;
}

select {
  background-color: var(--secondary-color);
  color: var(--text-color);
  border: 2px solid transparent;
  padding: 0.8rem 1.5rem;
  border-radius: 5px;
  cursor: pointer;
  margin-top: 1rem;
  background: linear-gradient(var(--secondary-color), var(--secondary-color)) padding-box,
              var(--primary-gradient) border-box;
}

select:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

select option {
  background-color: var(--secondary-color);
}

.import-controls {
  margin: 2rem 0;
  text-align: center;
}

#import-btn {
  background-color: var(--secondary-color);
}

.import-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin-top: 1rem;
}

.import-notification {
  position: fixed;
  top: 20px;
  right: 20px;
  padding: 1rem 2rem;
  border-radius: 5px;
  background: var(--primary-gradient);
  color: var(--text-color);
  z-index: 1000;
  animation: slideIn 0.3s ease-out, fadeOut 0.3s ease-out 2.7s forwards;
}

@keyframes slideIn {
  from {
    transform: translateX(100%);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

@keyframes fadeOut {
  from {
    opacity: 1;
  }
  to {
    opacity: 0;
  }
}

.hidden {
  display: none;
}

.edit-modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.8);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
}

.edit-modal.hidden {
  display: none;
}

.modal-content {
  background-color: var(--bg-color);
  padding: 2rem;
  border-radius: 10px;
  width: 80%;
  max-width: 800px;
  max-height: 80vh;
  overflow-y: auto;
}

.terms-editor table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
}

.terms-editor th,
.terms-editor td {
  padding: 0.5rem;
  text-align: left;
  border-bottom: 1px solid var(--secondary-color);
}

.terms-editor input {
  width: 100%;
  padding: 0.5rem;
  background-color: var(--secondary-color);
  border: none;
  color: var(--text-color);
  border-radius: 4px;
}

.json-editor {
  width: 100%;
  height: 400px;
  background-color: var(--secondary-color);
  color: var(--text-color);
  border: none;
  padding: 1rem;
  font-family: monospace;
  border-radius: 4px;
  resize: vertical;
}

.modal-buttons {
  display: flex;
  gap: 1rem;
  justify-content: flex-end;
  margin-top: 1rem;
}

.delete-term-btn {
  background-color: var(--accent-color);
  padding: 0.5rem 1rem;
}

#add-term-btn {
  background-color: var(--primary-color);
  padding: 0.5rem 1rem;
}

.feedback-buttons {
  display: none;
  gap: 1rem;
  justify-content: center;
  margin: 2rem 0;
}

.card.flipped + .feedback-buttons {
  display: flex;
}

.know-btn {
  background: linear-gradient(90deg, #4CAF50 0%, #45a049 100%);
}

.dont-know-btn {
  background: linear-gradient(90deg, #f44336 0%, #d32f2f 100%);
}