:root {
  --bg: #f7f9fc;
  --bg-secondary: #ffffff;
  --text-primary: #1a202c;
  --text-secondary: #4a5568;
  --accent: #3182ce;
  --accent-light: #ebf8ff;
  --correct: #38a169;
  --incorrect: #e53e3e;
  --border: #e2e8f0;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'Fira Code', 'Menlo', 'Consolas', 'Courier New', monospace;
  
  /* Liquid Toggle Variables for Light Mode */
  --toggle-bg: #e2e8f0;
  --toggle-handle-bg: var(--accent);
  --toggle-icon-fill: #ffffff;
}

body.dark {
  --bg: #1a202c;
  --bg-secondary: #2d3748;
  --text-primary: #f7fafc;
  --text-secondary: #a0aec0;
  --accent: #63b3ed;
  --accent-light: rgba(99, 179, 237, 0.1);
  --correct: #68d391;
  --incorrect: #fc8181;
  --border: #4a5568;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -1px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.25);
  
  /* Liquid Toggle Variables for Dark Mode */
  --toggle-bg: #4a5568;
  --toggle-handle-bg: var(--accent);
  --toggle-icon-fill: #ffffff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text-primary);
  font-family: var(--font-sans);
  transition: background 0.3s, color 0.3s;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.header {
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  padding: 1rem 2rem;
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 10;
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}
.logo span { color: var(--accent); }

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

.btn {
  padding: 0.6rem 1.2rem;
  border: 1px solid transparent;
  border-radius: 0.5rem;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 600;
  transition: all 0.2s ease-in-out;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: var(--accent);
  color: white;
  box-shadow: var(--shadow-sm);
}
.btn-primary:hover { filter: brightness(1.1); }

.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border-color: var(--border);
}
.btn-secondary:hover { background: var(--bg); border-color: var(--accent); color: var(--accent); }

/* --- Liquid Theme Toggle CSS --- */
.theme-toggle {
    position: relative;
    width: 64px;
    height: 32px;
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
}

.toggle-icons {
    position: absolute;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: space-around;
    align-items: center;
    z-index: 1; /* Place icons above the track */
}

.toggle-icons svg {
    width: 18px;
    height: 18px;
    fill: var(--toggle-icon-fill);
    transition: opacity 0.3s ease, transform 0.4s ease;
}

/* Light mode: Moon visible */
.toggle-icons .sun-icon {
    opacity: 0;
}
.toggle-icons .moon-icon {
    opacity: 1;
}

/* Dark mode: Sun visible */
body.dark .toggle-icons .sun-icon {
    opacity: 1;
}
body.dark .toggle-icons .moon-icon {
    opacity: 0;
}

.toggle-track {
    position: absolute;
    width: 100%;
    height: 100%;
    background: var(--toggle-bg);
    border-radius: 50px;
    transition: background-color 0.4s ease;
    /* Apply the SVG filter */
    filter: url(#liquid-goo);
}

.toggle-handle {
    position: absolute;
    top: 0;
    left: 0;
    width: 32px;
    height: 32px;
    background: var(--toggle-handle-bg);
    border-radius: 50%;
    transition: transform 0.4s cubic-bezier(0.45, 0, 0.2, 1);
}

body.dark .toggle-handle {
    transform: translateX(32px);
}


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

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.stat-card {
  background: var(--bg-secondary);
  padding: 1.5rem;
  border-radius: 0.75rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border);
  text-align: left;
}
.stat-value { font-size: 2.5rem; font-weight: 700; margin-bottom: 0.25rem; }
.stat-label { color: var(--text-secondary); font-size: 0.875rem; font-weight: 500; }

.main-card {
  background: var(--bg-secondary);
  border-radius: 0.75rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border);
  overflow: hidden;
}

.card-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.card-title { font-size: 1.5rem; font-weight: 600; margin: 0; }
.file-info { font-size: 0.875rem; color: var(--text-secondary); margin-top: 0.25rem; }

.tabs { display: flex; border-bottom: 1px solid var(--border); padding: 0 1.5rem; }
.tab {
  padding: 1rem 0.5rem;
  margin: 0 1rem;
  cursor: pointer;
  border: none;
  background: none;
  color: var(--text-secondary);
  font-weight: 600;
  transition: all 0.2s;
  border-bottom: 3px solid transparent;
}
.tab.active { color: var(--accent); border-bottom-color: var(--accent); }
.tab:first-child { margin-left: 0; }
.tab:hover { color: var(--accent); }

.tab-content { padding: 1.5rem; }

.typing-area {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  line-height: 2;
  height: 400px;
  overflow-y: auto;
  padding: 1rem;
  border-radius: 0.5rem;
  background: var(--bg);
  margin-bottom: 1.5rem;
  white-space: pre-wrap;
  word-wrap: break-word;
  position: relative;
  transition: all 0.3s;
}
.typing-area.active {
  box-shadow: 0 0 0 4px var(--accent-light);
}
.typing-line { padding: 0.25rem 0.5rem; border-radius: 0.25rem; transition: background-color 0.2s; }
.typing-line.current { background: var(--accent-light); }
.typing-line.completed { opacity: 0.5; }

.char { position: relative; border-radius: 2px; }
.char.correct { color: var(--correct); }
.char.incorrect { color: var(--incorrect); text-decoration: underline; text-decoration-thickness: 2px; }
.char.cursor::before {
  content: '';
  position: absolute;
  width: 2px;
  height: 1.5rem;
  background: var(--accent);
  animation: blink 1s infinite;
  top: 50%;
  transform: translateY(-50%);
}
@keyframes blink { 50% { opacity: 0; } }

.hidden-input { position: absolute; left: -9999px; opacity: 0; }
.progress-bar { width: 100%; height: 6px; background: var(--border); border-radius: 3px; overflow: hidden; margin-bottom: 1.5rem; }
.progress-fill { height: 100%; background: var(--accent); transition: width 0.3s ease; border-radius: 3px; }

.pagination { display: flex; justify-content: center; align-items: center; gap: 1rem; margin-top: 1.5rem; }

.library-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 1.5rem; }
.book-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  overflow: hidden;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}
.book-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.book-cover { width: 100%; height: 150px; background: var(--border); display: flex; align-items: center; justify-content: center; }
.book-cover img { width: 100%; height: 100%; object-fit: cover; }
.book-info { padding: 1rem; }
.book-title { font-weight: 600; margin-bottom: 0.25rem; }
.book-author { font-size: 0.875rem; color: var(--text-secondary); }

.hidden { display: none; }

.file-input { display: none; }
.upload-area {
  border: 2px dashed var(--border);
  border-radius: 0.5rem;
  padding: 3rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
}
.upload-area:hover { border-color: var(--accent); background: var(--accent-light); }
.upload-icon { font-size: 3rem; margin-bottom: 1rem; opacity: 0.5; }

.start-hint {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(0,0,0,0.5);
    color: white;
    padding: 1.5rem 2.5rem;
    border-radius: 0.5rem;
    font-size: 1.1rem;
    font-weight: 500;
    pointer-events: none;
    backdrop-filter: blur(5px);
}

@media (max-width: 768px) {
  .container { padding: 0 1rem; margin-top: 1rem; }
  .header-content { flex-direction: column; gap: 1rem; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .typing-area { font-size: 1rem; }
  .library-grid { grid-template-columns: 1fr 1fr; }
}