/* ===== RESET & VARIABLES ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #0f0f1a;
  --bg-card: #1a1a2e;
  --bg-hover: #222240;
  --bg-input: #16162b;
  --text: #e8e8f0;
  --text-muted: #8888a8;
  --primary: #6c5ce7;
  --primary-hover: #7c6ef7;
  --primary-glow: rgba(108, 92, 231, 0.3);
  --success: #00cec9;
  --success-bg: rgba(0, 206, 201, 0.15);
  --error: #ff6b6b;
  --error-bg: rgba(255, 107, 107, 0.15);
  --warning: #feca57;
  --warning-bg: rgba(254, 202, 87, 0.15);
  --border: #2a2a45;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --transition: 0.2s ease;
}

[data-theme="light"] {
  --bg: #f5f5fa;
  --bg-card: #ffffff;
  --bg-hover: #eeeef5;
  --bg-input: #f0f0f8;
  --text: #1a1a2e;
  --text-muted: #6666880;
  --border: #dddde8;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
}

html {
  font-size: 16px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ===== HEADER ===== */
.header {
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary), var(--success));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.header-actions {
  display: flex;
  gap: 0.5rem;
}

.icon-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  padding: 0.5rem;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
}

.icon-btn:hover {
  background: var(--bg-hover);
  color: var(--text);
}

.icon-btn.active {
  color: var(--primary);
  border-color: var(--primary);
}

/* ===== SCREENS ===== */
.screen {
  display: none;
  animation: fadeIn 0.3s ease;
}

.screen.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== IMPORT SCREEN ===== */
.import-container {
  max-width: 640px;
  margin: 0 auto;
  padding: 3rem 1.5rem;
}

.import-hero {
  text-align: center;
  margin-bottom: 2rem;
}

.import-hero h2 {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.import-hero p {
  color: var(--text-muted);
  font-size: 1.05rem;
}

.import-tabs {
  display: flex;
  gap: 0;
  margin-bottom: 1.5rem;
  background: var(--bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  overflow: hidden;
}

.tab-btn {
  flex: 1;
  padding: 0.75rem;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}

.tab-btn.active {
  background: var(--primary);
  color: white;
}

.tab-btn:not(.active):hover {
  background: var(--bg-hover);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

.input-group {
  display: flex;
  gap: 0.5rem;
}

.input-group input {
  flex: 1;
}

input[type="url"],
input[type="text"],
textarea {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.85rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  outline: none;
  transition: var(--transition);
  width: 100%;
}

input:focus,
textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

textarea {
  min-height: 200px;
  resize: vertical;
  font-family: inherit;
  margin-bottom: 1rem;
}

.status-msg {
  margin-top: 0.75rem;
  font-size: 0.9rem;
  min-height: 1.4rem;
}

.status-msg.error { color: var(--error); }
.status-msg.success { color: var(--success); }
.status-msg.loading { color: var(--text-muted); }

/* ===== BUTTONS ===== */
.btn-primary {
  background: var(--primary);
  color: white;
  border: none;
  padding: 0.85rem 1.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  white-space: nowrap;
}

.btn-primary:hover {
  background: var(--primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px var(--primary-glow);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-primary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.btn-lg {
  padding: 1rem 2.5rem;
  font-size: 1.05rem;
  border-radius: var(--radius);
}

.btn-ghost {
  background: none;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  cursor: pointer;
  transition: var(--transition);
}

.btn-ghost:hover {
  background: var(--bg-hover);
}

/* ===== SAVED SETS ===== */
.saved-sets {
  margin-top: 2.5rem;
}

.saved-sets h3 {
  font-size: 1rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.saved-set-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.85rem 1rem;
  margin-bottom: 0.5rem;
  cursor: pointer;
  transition: var(--transition);
}

.saved-set-item:hover {
  border-color: var(--primary);
  background: var(--bg-hover);
}

.saved-set-info {
  display: flex;
  flex-direction: column;
}

.saved-set-title {
  font-weight: 600;
  font-size: 0.95rem;
}

.saved-set-meta {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.saved-set-actions {
  display: flex;
  gap: 0.5rem;
}

.btn-delete-set {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.25rem;
  font-size: 1.1rem;
  transition: var(--transition);
}

.btn-delete-set:hover {
  color: var(--error);
}

/* ===== OVERVIEW SCREEN ===== */
.overview-container {
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

.overview-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.overview-header h2 {
  font-size: 1.5rem;
  flex: 1;
}

.badge {
  background: var(--primary);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 600;
}

/* Editable title */
.editable-title {
  cursor: pointer;
  border-bottom: 2px dashed transparent;
  transition: var(--transition);
}

.editable-title:hover {
  border-bottom-color: var(--primary);
}

.title-edit-input {
  font-size: 1.5rem;
  font-weight: 700;
  flex: 1;
  padding: 0.25rem 0.5rem;
}

/* Terms toolbar */
.terms-toolbar {
  display: flex;
  justify-content: flex-end;
  margin-bottom: 0.5rem;
  gap: 0.5rem;
}

.btn-sm {
  padding: 0.4rem 0.85rem;
  font-size: 0.8rem;
}

.terms-preview {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  max-height: 400px;
  overflow-y: auto;
  margin-bottom: 2rem;
}

.term-row {
  display: flex;
  align-items: center;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
  gap: 0.75rem;
}

.term-row:last-child {
  border-bottom: none;
}

.term-row .term-word {
  font-weight: 600;
  flex: 1;
  min-width: 0;
}

.term-row .term-def {
  color: var(--text-muted);
  flex: 2;
  min-width: 0;
}

.term-row .term-actions {
  display: flex;
  gap: 0.25rem;
  flex-shrink: 0;
  opacity: 0;
  transition: var(--transition);
}

.term-row:hover .term-actions {
  opacity: 1;
}

.term-action-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  padding: 0.2rem 0.45rem;
  cursor: pointer;
  font-size: 0.75rem;
  transition: var(--transition);
}

.term-action-btn:hover {
  background: var(--bg-hover);
  color: var(--text);
}

.term-action-btn.delete:hover {
  color: var(--error);
  border-color: var(--error);
}

/* Inline term editing */
.term-row.editing {
  flex-wrap: wrap;
  background: var(--bg-hover);
}

.term-row.editing .term-edit-input {
  flex: 1;
  min-width: 100px;
  padding: 0.4rem 0.6rem;
  font-size: 0.9rem;
}

.term-row.editing .term-edit-actions {
  display: flex;
  gap: 0.35rem;
  width: 100%;
  margin-top: 0.35rem;
  justify-content: flex-end;
}

/* Add term row */
.add-term-row {
  display: flex;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--border);
  background: var(--bg-hover);
  border-radius: 0 0 var(--radius) var(--radius);
}

.add-term-row input {
  flex: 1;
  padding: 0.5rem 0.65rem;
  font-size: 0.85rem;
}

.add-term-row button {
  flex-shrink: 0;
}

.study-options {
  margin-bottom: 2rem;
}

.study-options h3 {
  font-size: 1rem;
  margin-bottom: 1rem;
  color: var(--text-muted);
}

.options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
}

.option-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
}

.option-card > label {
  font-weight: 600;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  display: block;
  margin-bottom: 0.75rem;
}

.checkbox-group,
.radio-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.checkbox-label,
.radio-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  cursor: pointer;
}

input[type="checkbox"],
input[type="radio"] {
  accent-color: var(--primary);
  width: 1rem;
  height: 1rem;
}

#btn-start-learn {
  display: block;
  width: 100%;
  max-width: 400px;
  margin: 0 auto;
}

/* ===== LEARN SCREEN ===== */
.learn-container {
  max-width: 700px;
  margin: 0 auto;
  padding: 1.5rem;
}

.progress-section {
  margin-bottom: 2rem;
}

.progress-bar {
  height: 8px;
  background: var(--bg-card);
  border-radius: 999px;
  overflow: hidden;
  border: 1px solid var(--border);
  margin-bottom: 0.75rem;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--success));
  border-radius: 999px;
  transition: width 0.5s ease;
  width: 0%;
}

.progress-stats {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.stat {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.stat strong {
  color: var(--text);
}

.stat-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.stat-dot.mastered { background: var(--success); }
.stat-dot.learning { background: var(--warning); }
.stat-dot.remaining { background: var(--text-muted); }

/* Question Area */
.question-area {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow);
}

.question-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}

.type-badge {
  background: var(--primary-glow);
  color: var(--primary);
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 600;
}

[data-theme="light"] .type-badge {
  background: rgba(108, 92, 231, 0.1);
}

.question-counter {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.question-prompt {
  font-size: 1.3rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  line-height: 1.5;
}

/* Multiple Choice */
.mc-options {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.mc-option {
  background: var(--bg-input);
  border: 2px solid var(--border);
  color: var(--text);
  padding: 1rem 1.25rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  text-align: left;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.mc-option:hover:not(.disabled) {
  border-color: var(--primary);
  background: var(--bg-hover);
}

.mc-option .option-letter {
  background: var(--border);
  color: var(--text-muted);
  width: 28px;
  height: 28px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.8rem;
  flex-shrink: 0;
}

.mc-option.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.mc-option.correct .option-letter {
  background: var(--success);
  color: white;
}

.mc-option.incorrect {
  border-color: var(--error);
  background: var(--error-bg);
}

.mc-option.incorrect .option-letter {
  background: var(--error);
  color: white;
}

.mc-option.disabled {
  cursor: default;
  opacity: 0.6;
}

.mc-option.correct.disabled {
  opacity: 1;
}

/* True/False */
.tf-options {
  display: flex;
  gap: 1rem;
}

.tf-btn {
  flex: 1;
  padding: 1.25rem;
  background: var(--bg-input);
  border: 2px solid var(--border);
  color: var(--text);
  border-radius: var(--radius-sm);
  font-size: 1.1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.tf-btn:hover:not(.disabled) {
  border-color: var(--primary);
}

.tf-btn.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.tf-btn.incorrect {
  border-color: var(--error);
  background: var(--error-bg);
}

.tf-btn.disabled {
  cursor: default;
  opacity: 0.6;
}

.tf-btn.correct.disabled {
  opacity: 1;
}

/* Written */
.written-input {
  display: flex;
  gap: 0.5rem;
}

.written-input input {
  flex: 1;
  font-size: 1.05rem;
  padding: 1rem;
}

/* Feedback */
.feedback {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
  text-align: center;
}

.feedback-icon {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
}

.feedback-text {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.feedback-correct {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.feedback.correct .feedback-text { color: var(--success); }
.feedback.incorrect .feedback-text { color: var(--error); }

.feedback-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  align-items: center;
}

/* ===== RESULTS SCREEN ===== */
.results-container {
  max-width: 700px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

.results-hero {
  text-align: center;
  margin-bottom: 2rem;
}

.results-icon {
  font-size: 3rem;
  margin-bottom: 0.5rem;
}

.results-hero h2 {
  font-size: 1.75rem;
  margin-bottom: 0.25rem;
}

.results-hero p {
  color: var(--text-muted);
}

.results-stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1rem;
  margin-bottom: 2rem;
}

.result-stat {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  text-align: center;
}

.result-number {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--primary);
}

.result-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

.results-breakdown {
  margin-bottom: 2rem;
}

.results-breakdown h3 {
  font-size: 1rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.results-terms-list {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.result-term-row {
  display: flex;
  align-items: center;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
  gap: 0.75rem;
  font-size: 0.9rem;
}

.result-term-row:last-child {
  border-bottom: none;
}

.result-term-status {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
}

.result-term-status.mastered { background: var(--success); }
.result-term-status.learning { background: var(--warning); }
.result-term-status.not-started { background: var(--text-muted); }

.result-term-word {
  font-weight: 600;
  flex: 1;
}

.result-term-score {
  color: var(--text-muted);
  font-size: 0.8rem;
}

.results-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 600px) {
  .results-stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .options-grid {
    grid-template-columns: 1fr;
  }

  .input-group {
    flex-direction: column;
  }

  .tf-options {
    flex-direction: column;
  }

  .question-prompt {
    font-size: 1.1rem;
  }

  .written-input {
    flex-direction: column;
  }

  .progress-stats {
    gap: 1rem;
  }
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: var(--bg);
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 999px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

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

.shake {
  animation: shake 0.3s ease;
}

@keyframes pop {
  0% { transform: scale(1); }
  50% { transform: scale(1.05); }
  100% { transform: scale(1); }
}

.pop {
  animation: pop 0.3s ease;
}

/* Loading spinner */
.spinner {
  display: inline-block;
  width: 16px;
  height: 16px;
  border: 2px solid var(--text-muted);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
  margin-right: 0.5rem;
  vertical-align: middle;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}