:root {
  --glaucous: #6279b8;
  --dusk-blue: #49516f;
  --deep-teal: #496f5d;
  --shamrock: #4c9f70;

  --color-primary: var(--glaucous);
  --color-primary-dark: var(--dusk-blue);
  --color-primary-light: #a0b4d4;
  --color-bg: #f0f4f9;
  --color-surface: #ffffff;
  --color-text: #2d3a4f;
  --color-text-muted: #6b7a94;
  --color-border: #c5d0e0;
  --color-generada: #d8dde5;
  --color-success: var(--shamrock);
  --color-fondo-elemento: var(--glaucous);
  
  --font-family: system-ui, -apple-system, sans-serif;
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
}

[data-theme="dark"] {
  --color-primary: #8fa4d4;
  --color-primary-dark: #6b82a8;
  --color-primary-light: #4a5c82;
  --color-bg: #1a1d29;
  --color-surface: #252a3a;
  --color-text: #e2e8f0;
  --color-text-muted: #fff;
  --color-border: #3d4559;
  --color-generada: #979595;
  --color-fondo-elemento: #8fa4d4;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.3);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.4);
}

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

body {
  font-family: var(--font-family);
  background-color: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: var(--spacing-md);
  position: relative;
  overflow-x: hidden;
}

.fondo-letras {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: -1;
  overflow: hidden;
}

.fondo-letras span {
  position: absolute;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-fondo-elemento);
  opacity: 0.12;
  user-select: none;
}

.container {
  width: 100%;
  max-width: 600px;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.header {
  text-align: center;
  padding: var(--spacing-md) 0;
}

.title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-primary);
}

.main {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-lg);
}

.letra-display {
  width: 100%;
  height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-surface);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
}

.letra-principal {
  font-size: 8rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
  animation: none;
}

.letra-principal.animate {
  animation: popIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

@keyframes popIn {
  0% {
    opacity: 0;
    transform: scale(0.5);
  }
  100% {
    opacity: 1;
    transform: scale(1);
  }
}

.btn {
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
  min-height: 48px;
}

.btn:focus-visible {
  outline: 3px solid var(--color-primary-light);
  outline-offset: 2px;
}

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

.btn-primary:hover:not(:disabled) {
  background: var(--color-primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
}

.btn-primary:disabled {
  background: var(--color-generada);
  cursor: not-allowed;
}

.btn-secondary {
  background: transparent;
  color: var(--color-text-muted);
  border: 2px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-text-muted);
  color: var(--color-text);
}

.mensaje-fin {
  background: #e8f5ee;
  color: var(--deep-teal);
  padding: var(--spacing-md);
  border-radius: var(--border-radius-sm);
  text-align: center;
  font-weight: 500;
  animation: fadeIn 0.3s ease;
  border: 1px solid var(--color-border);
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}

.pool-letras {
  width: 100%;
}

.pool-title {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-sm);
  text-align: center;
}

.grid-letras {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--spacing-xs);
  max-width: 400px;
  margin: 0 auto;
}

.letra-item {
  width: calc((100% - 4 * var(--spacing-xs)) / 5);
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-sm);
  font-weight: 600;
  font-size: 0.875rem;
  transition: all 0.2s ease;
}

.letra-item.generada {
  background: var(--color-generada);
  color: var(--color-text-muted);
  text-decoration: line-through;
  opacity: 0.6;
}

.footer {
  text-align: center;
  /* padding: var(--spacing-md) 0; */
}

#contador {
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.mode-switch {
  margin-top: var(--spacing-md);
}

.switch-label {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  cursor: pointer;
}

.switch-input {
  display: none;
}

.switch-slider {
  width: 48px;
  height: 26px;
  background: var(--color-border);
  border-radius: 13px;
  position: relative;
  transition: background 0.3s;
}

.switch-slider::before {
  content: '';
  position: absolute;
  width: 20px;
  height: 20px;
  background: white;
  border-radius: 50%;
  top: 3px;
  left: 3px;
  transition: transform 0.3s;
  box-shadow: 0 2px 4px rgb(0 0 0 / 0.2);
}

.switch-input:checked + .switch-slider {
  background: var(--color-primary);
}

.switch-input:checked + .switch-slider::before {
  transform: translateX(22px);
}

.switch-option {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text-muted);
  transition: color 0.3s;
}

.switch-input:checked ~ .switch-option[data-mode="numeros"],
.switch-option[data-mode="letras"]:not(:has(~ .switch-input:checked)) {
  color: var(--color-primary);
}

.rango-config {
  margin-top: var(--spacing-md);
}

.rango-opcion label {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.input-numero {
  width: 70px;
  padding: var(--spacing-sm);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-sm);
  font-size: 1rem;
  text-align: center;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
}

.input-numero:focus {
  outline: none;
  border-color: var(--color-primary);
}

.input-letras {
  padding: var(--spacing-sm);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-sm);
  font-size: 1rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
}

.input-letras:focus {
  outline: none;
  border-color: var(--color-primary);
}

.theme-switch {
  position: absolute;
  top: var(--spacing-md);
  right: var(--spacing-md);
}

.btn-theme {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 50%;
  width: 44px;
  height: 44px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  transition: all 0.2s ease;
}

.btn-theme:hover {
  background: var(--color-border);
}

.btn-theme:focus-visible {
  outline: 3px solid var(--color-primary-light);
  outline-offset: 2px;
}

.icono-sol {
  display: block;
}

.icono-luna {
  display: none;
}

[data-theme="dark"] .icono-sol {
  display: none;
}

[data-theme="dark"] .icono-luna {
  display: block;
}

[data-theme="dark"] .mensaje-fin {
  background: #1e3329;
  color: #7ecba1;
}

@media (min-width: 768px) {
  :root {
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
  }

  .title {
    font-size: 2rem;
  }

  .letra-display {
    height: 280px;
  }

  .letra-principal {
    font-size: 12rem;
  }

  .grid-letras {
    gap: var(--spacing-sm);
    max-width: 500px;
  }

  .letra-item {
    width: calc((100% - 9 * var(--spacing-sm)) / 10);
    font-size: 1rem;
  }
}