@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

/* === CSS Reset === */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

input,
button,
textarea,
select {
  font: inherit;
  outline: none;
}

p,
h1,
h2,
h3,
h4,
h5,
h6 {
  overflow-wrap: break-word;
}

a {
  text-decoration: none;
  color: inherit;
}

/* === Design System Variables (Light Mode) === */
:root {
  /* --- COLORES --- */
  --color-primary: #5a7dff; /* Azul vibrante pero suave */
  --color-primary-light: #8ba5ff;
  --color-primary-dark: #3a5aff;
  --color-secondary: #00c7b7; /* Teal de acento */
  --color-accent: #ffb74d; /* Naranja suave para destacar */

  --color-text-primary: #2d3748; /* Gris oscuro para texto principal */
  --color-text-secondary: #4a5568; /* Gris medio para texto secundario */
  --color-text-muted: #718096; /* Gris claro para texto de ayuda */
  --color-text-on-primary: #ffffff;

  --color-bg: #f0f4f8; /* Fondo principal muy claro */
  --color-bg-alt: #e2e8f0; /* Fondo alternativo para cards/secciones */
  --color-surface: #ffffff; /* Superficie principal (cards, modales) */
  --color-border: #cbd5e0; /* Borde sutil */
  --color-divider: #e2e8f0;

  --color-success: #48bb78;
  --color-warning: #ecc94b;
  --color-error: #ef4444;

  /* --- TIPOGRAFÍA --- */
  --font-family-base: 'Inter', sans-serif;
  --font-family-heading: 'Inter', sans-serif;

  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem; /* 16px */
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;

  --font-weight-light: 300;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  --line-height-base: 1.6;
  --line-height-heading: 1.2;

  /* --- ESPACIADO --- */
  --spacing-xxs: 4px;
  --spacing-xs: 8px;
  --spacing-sm: 12px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --spacing-2xl: 48px;
  --spacing-3xl: 64px;

  /* --- BORDER RADIUS --- */
  --border-radius-xs: 4px;
  --border-radius-sm: 8px;
  --border-radius-md: 12px;
  --border-radius-lg: 16px;
  --border-radius-xl: 24px;
  --border-radius-full: 9999px;

  /* --- SOMBRAS --- */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1), 0 2px 4px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.12), 0 4px 6px rgba(0, 0, 0, 0.08);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.15), 0 10px 10px rgba(0, 0, 0, 0.08);
  --shadow-glass: 0 8px 32px 0 rgba(31, 38, 135, 0.37);

  /* --- TRANSICIONES --- */
  --transition-ease: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* === Dark Mode Variables === */
:root.dark,
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #6a8dff;
    --color-primary-light: #9ab5ff;
    --color-primary-dark: #4a6aff;
    --color-secondary: #00e0d0;
    --color-accent: #ffc76d;

    --color-text-primary: #e2e8f0;
    --color-text-secondary: #cbd5e0;
    --color-text-muted: #a0aec0;
    --color-text-on-primary: #ffffff;

    --color-bg: #1a202c;
    --color-bg-alt: #2d3748;
    --color-surface: #242c38;
    --color-border: #4a5568;
    --color-divider: #3a4452;

    --color-success: #68d391;
    --color-warning: #f6e05e;
    --color-error: #fc8181;

    --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.2);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.25), 0 1px 2px rgba(0, 0, 0, 0.15);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.3), 0 2px 4px rgba(0, 0, 0, 0.18);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.35), 0 4px 6px rgba(0, 0, 0, 0.25);
    --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.4), 0 10px 10px rgba(0, 0, 0, 0.25);
    --shadow-glass: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
  }
}

/* === Base Styles === */
body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  color: var(--color-text-primary);
  background: linear-gradient(135deg, var(--color-bg), var(--color-bg-alt));
  min-height: 100vh;
  display: flex; /* Para centrar el app-card */
  justify-content: center;
  align-items: flex-start; /* Alineación superior para permitir scroll */
  padding: var(--spacing-xl) var(--spacing-md); /* Padding para móviles */
  transition: var(--transition-ease);
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-family-heading);
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-heading);
  color: var(--color-text-primary);
  margin-bottom: var(--spacing-md);
}

h1 { font-size: var(--font-size-3xl); }
h2 { font-size: var(--font-size-2xl); }
h3 { font-size: var(--font-size-xl); }
h4 { font-size: var(--font-size-lg); }
h5 { font-size: var(--font-size-base); }
h6 { font-size: var(--font-size-sm); }

p {
  margin-bottom: var(--spacing-sm);
}

a {
  color: var(--color-primary);
  transition: var(--transition-ease);
}

a:hover,
a:focus {
  color: var(--color-primary-dark);
  text-decoration: underline;
}

/* === Layout Helpers === */
.container {
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--spacing-md);
  padding-right: var(--spacing-md);
}

.flex {
  display: flex;
  gap: var(--spacing-md);
}

.flex-col {
  flex-direction: column;
}

.flex-row {
  flex-direction: row;
}

.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.align-center { align-items: center; }
.align-start { align-items: flex-start; }
.align-end { align-items: flex-end; }

.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid-cols-3 { grid-template-columns: repeat(3, 1fr); }

.section {
  padding-top: var(--spacing-2xl);
  padding-bottom: var(--spacing-2xl);
}

/* === Utility Classes === */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

/* === Component Styles === */

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--border-radius-md);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  cursor: pointer;
  border: 1px solid transparent;
  transition: var(--transition-ease);
  user-select: none;
  gap: var(--spacing-xs);
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

.btn:active {
  transform: translateY(0);
  box-shadow: var(--shadow-xs);
  animation: pulse 0.3s ease-out;
}

.btn-primary {
  background-color: var(--color-primary);
  color: var(--color-text-on-primary);
  border-color: var(--color-primary);
}

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

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

.btn-secondary:hover {
  background-color: var(--color-secondary); /* Mantener color, solo sombra/transform */
}

.btn-ghost {
  background-color: transparent;
  color: var(--color-text-secondary);
  border-color: transparent;
}

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

.btn-icon {
  padding: var(--spacing-xs);
  width: 40px;
  height: 40px;
  border-radius: var(--border-radius-md);
}

/* --- Inputs --- */
.input-group {
  display: flex;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
}

.input,
textarea,
select {
  width: 100%;
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-md);
  background-color: var(--color-surface);
  color: var(--color-text-primary);
  transition: var(--transition-ease);
}

.input::placeholder {
  color: var(--color-text-muted);
}

.input:focus,
textarea:focus,
select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(var(--color-primary-dark), 0.2); /* Soft focus ring */
}

/* --- Cards / Glassmorphism Container --- */
.app-card {
  width: 100%;
  max-width: 640px; /* Desktop */
  background: rgba(var(--color-surface-rgb, 255, 255, 255), 0.7); /* Usar RGB para glassmorphism */
  border-radius: var(--border-radius-xl);
  border: 1px solid rgba(var(--color-border-rgb, 203, 213, 224), 0.3);
  box-shadow: var(--shadow-glass);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: clamp(var(--spacing-lg), 5vw, var(--spacing-2xl));
  margin-top: var(--spacing-xl); /* Espacio superior para el card */
  margin-bottom: var(--spacing-xl);
  animation: fadeIn 0.5s ease-out;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

/* --- Badges --- */
.badge {
  display: inline-flex;
  align-items: center;
  padding: var(--spacing-xxs) var(--spacing-xs);
  border-radius: var(--border-radius-full);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-on-primary);
  background-color: var(--color-primary);
}

.badge-success { background-color: var(--color-success); }
.badge-warning { background-color: var(--color-warning); }
.badge-error { background-color: var(--color-error); }
.badge-secondary { background-color: var(--color-secondary); }

/* --- Task List Specific Styles --- */
.task-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.task-item {
  display: flex;
  align-items: center;
  background-color: var(--color-surface);
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--border-radius-md);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-xs);
  transition: var(--transition-ease);
  animation: slideUp 0.3s ease-out forwards;
}

.task-item.completed {
  opacity: 0.7;
  background-color: var(--color-bg-alt);
  border-color: var(--color-divider);
}

.task-item-checkbox {
  appearance: none;
  width: 20px;
  height: 20px;
  min-width: 20px;
  border: 2px solid var(--color-border);
  border-radius: var(--border-radius-xs);
  margin-right: var(--spacing-md);
  cursor: pointer;
  display: grid;
  place-content: center;
  transition: var(--transition-ease);
}

.task-item-checkbox::before {
  content: "";
  width: 12px;
  height: 12px;
  transform: scale(0);
  transition: 120ms transform ease-in-out;
  box-shadow: inset 1em 1em var(--color-text-on-primary);
  background-color: var(--color-primary);
  transform-origin: bottom left;
  clip-path: polygon(14% 44%, 0 65%, 50% 100%, 100% 16%, 80% 0%, 43% 60%);
  border-radius: 2px;
}

.task-item-checkbox:checked {
  border-color: var(--color-primary);
  background-color: var(--color-primary);
}

.task-item-checkbox:checked::before {
  transform: scale(1);
}

.task-item-text {
  flex-grow: 1;
  color: var(--color-text-primary);
  font-size: var(--font-size-base);
  transition: var(--transition-ease);
}

.task-item.completed .task-item-text {
  text-decoration: line-through;
  color: var(--color-text-muted);
}

.task-item-delete {
  background: none;
  border: none;
  color: var(--color-text-muted);
  font-size: var(--font-size-lg);
  cursor: pointer;
  margin-left: var(--spacing-md);
  transition: var(--transition-ease);
  padding: var(--spacing-xs);
  border-radius: var(--border-radius-sm);
}

.task-item-delete:hover {
  color: var(--color-error);
  background-color: rgba(var(--color-error-rgb, 239, 68, 68), 0.1);
}


/* === Animations === */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(0.98); }
  100% { transform: scale(1); }
}

/* === Responsive Design === */
@media (min-width: 768px) {
  body {
    padding: var(--spacing-2xl);
    align-items: center; /* Centrar verticalmente en desktop */
  }

  h1 { font-size: var(--font-size-4xl); }
  h2 { font-size: var(--font-size-3xl); }

  .app-card {
    padding: var(--spacing-3xl);
    margin-top: 0;
    margin-bottom: 0;
  }

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

@media (max-width: 767px) {
  .input-group {
    flex-direction: column;
  }
  .btn {
    width: 100%;
  }
  .task-item-delete {
    margin-left: auto; /* Empujar el botón de eliminar a la derecha */
  }
}

/* Definiciones de RGB para Glassmorphism en Dark Mode */
:root.dark {
  --color-surface-rgb: 36, 44, 56;
  --color-border-rgb: 74, 85, 104;
  --color-error-rgb: 252, 129, 129;
}
:root {
  --color-surface-rgb: 255, 255, 255;
  --color-border-rgb: 203, 213, 224;
  --color-error-rgb: 239, 68, 68;
}