/* ===== VARIABLES GLOBALES ===== */
:root {
  --primary-color: #2563eb;
  --primary-dark: #1e40af;
  --secondary-color: #64748b;
  --success-color: #10b981;
  --danger-color: #ef4444;
  --warning-color: #f59e0b;
  --light-bg: #f8fafc;
  --card-bg: #ffffff;
  --border-color: #e2e8f0;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --radius: 8px;
  --radius-lg: 12px;
  --transition: 0.3s ease all;
}

/* ===== RESET Y ESTILOS BASE ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, sans-serif;
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  padding: 2rem 1rem;
}

/* Gradiente solo para ejercicios que NO sean el 1 */
body:not(:has(.container)) {
  background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
}

/* ===== CONTENEDOR PRINCIPAL ===== */
.container {
  max-width: 900px;
  margin: 0 auto;
  width: 100%;
}

/* Contenedor más pequeño solo para ejercicio 1 (sin menú) */
.container:not(:has(.menu)) {
  max-width: 420px;
}

/* ===== TARJETAS ===== */
.card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-lg);
  margin-bottom: 2rem;
  border: 1px solid var(--border-color);
}

/* ===== TIPOGRAFÍA ===== */
h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  color: var(--text-primary);
  text-align: center;
}

h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.75rem;
  color: var(--text-primary);
}

p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

/* ===== MENÚ PRINCIPAL ===== */
.menu {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 2rem;
}

.menu li {
  margin: 0;
}

.menu a {
  display: block;
  padding: 1rem 1.5rem;
  background: linear-gradient(
    135deg,
    var(--primary-color) 0%,
    var(--primary-dark) 100%
  );
  color: white;
  text-decoration: none;
  border-radius: var(--radius-lg);
  font-weight: 600;
  text-align: center;
  transition: var(--transition);
  box-shadow: var(--shadow);
  border: none;
}

.menu a:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, var(--primary-dark) 0%, #1e3a8a 100%);
}

.menu a:active {
  transform: translateY(-1px);
}

/* ===== BOTONES ===== */
button,
.action-btn {
  padding: 0.75rem 1.5rem;
  background: var(--primary-color);
  color: white;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow);
  display: inline-block;
  margin: 0.5rem 0.5rem 0.5rem 0;
}

button:hover,
.action-btn:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

button:active,
.action-btn:active {
  transform: translateY(0);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Variantes de botones */
#addItemBtn,
#countBtn,
#addBtn,
#subBtn,
#mulBtn,
#divBtn {
  background: var(--primary-color);
}

#addItemBtn:hover,
#countBtn:hover,
#addBtn:hover,
#subBtn:hover,
#mulBtn:hover,
#divBtn:hover {
  background: var(--primary-dark);
}

/* ===== INPUTS Y FORMULARIOS ===== */
input[type="text"],
input[type="number"],
input[type="email"],
input[type="password"],
input[type="date"],
select,
textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 1rem;
  background: var(--light-bg);
  color: var(--text-primary);
  transition: var(--transition);
  font-family: inherit;
  margin-bottom: 1rem;
}

input[type="text"]:focus,
input[type="number"]:focus,
input[type="email"]:focus,
input[type="password"]:focus,
input[type="date"]:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  background: white;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ===== CONTENIDO DE EJERCICIOS ===== */
.exercise-content {
  background: var(--light-bg);
  padding: 2rem;
  border-radius: var(--radius);
  margin: 1.5rem 0;
  border-left: 4px solid var(--primary-color);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
  justify-content: center;
}

/* ===== LISTAS ===== */
ul,
ol {
  margin-left: 1.5rem;
  margin-bottom: 1rem;
}

li {
  margin-bottom: 0.5rem;
  color: var(--text-secondary);
}

/* ===== BOTÓN X DE TAREAS (EJERCICIO 9) ===== */
#taskList {
  list-style: none;
}

#taskList li {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  background: white;
  margin-bottom: 0.5rem;
  border-radius: var(--radius);
  border-left: 3px solid var(--primary-color);
  color: var(--text-secondary);
}

#taskList li::before {
  content: "●";
  color: var(--primary-color);
  font-size: 1.2rem;
  line-height: 1;
  margin-right: 0.5rem;
  flex-shrink: 0;
}

#taskList button {
  font-size: 0.7rem;
  padding: 0.15rem 0.6rem;
  margin-left: auto;
  border-radius: 4px;
  background: var(--primary-color);
  color: #fff;
  font-weight: 700;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: none;
  cursor: pointer;
  vertical-align: middle;
  line-height: 1;
  flex-shrink: 0;
}

#taskList button:hover {
  background: var(--danger-color);
  transform: scale(1.1);
}

#itemList {
  background: var(--light-bg);
  padding: 1rem;
  border-radius: var(--radius);
  margin-top: 1rem;
  list-style-position: inside;
}

#itemList li {
  padding: 0.75rem;
  background: white;
  margin-bottom: 0.5rem;
  border-radius: var(--radius);
  border-left: 3px solid var(--primary-color);
  padding-left: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* ===== RESULTADOS Y OUTPUTS ===== */
#counter,
#result {
  background: var(--light-bg);
  padding: 1rem;
  border-radius: var(--radius);
  font-weight: 600;
  color: var(--primary-color);
  font-size: 1.1rem;
  border-left: 4px solid var(--primary-color);
}

/* ===== ENLACES DE VOLVER ===== */
.back {
  display: inline-block;
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-color);
}

.back a {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 600;
  transition: var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.back a:hover {
  color: var(--primary-dark);
  transform: translateX(-3px);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  body {
    padding: 1rem;
  }

  .card {
    padding: 1.5rem;
  }

  h1 {
    font-size: 1.5rem;
  }

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

  .exercise-content {
    padding: 1.5rem;
  }

  input[type="text"],
  input[type="number"],
  button {
    width: 100%;
  }

  button {
    margin: 0.5rem 0;
  }
}

@media (max-width: 480px) {
  body {
    padding: 0.5rem;
  }

  .card {
    padding: 1rem;
  }

  h1 {
    font-size: 1.25rem;
  }

  button,
  .action-btn {
    padding: 0.6rem 1rem;
    font-size: 0.9rem;
  }
}

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

.card {
  animation: fadeIn 0.5s ease;
}

/* ===== UTILITIES ===== */
.text-center {
  text-align: center;
}

.text-primary {
  color: var(--primary-color);
}

.text-success {
  color: var(--success-color);
}

.text-danger {
  color: var(--danger-color);
}

.mt-1 {
  margin-top: 0.5rem;
}
.mt-2 {
  margin-top: 1rem;
}
.mt-3 {
  margin-top: 1.5rem;
}

.mb-1 {
  margin-bottom: 0.5rem;
}
.mb-2 {
  margin-bottom: 1rem;
}
.mb-3 {
  margin-bottom: 1.5rem;
}

.p-1 {
  padding: 0.5rem;
}
.p-2 {
  padding: 1rem;
}
.p-3 {
  padding: 1.5rem;
}
/* ===== FIX LISTA DE TAREAS (GitHub Pages) ===== */

#taskList {
  list-style: none;
  padding: 0;
  margin: 30px 0;
}

#taskList li {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.05);
  margin-bottom: 10px;
}

#taskList li::marker {
  content: none;
}

#taskList input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
}