/* Reset básico */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

/* BODY */
body {
  background: linear-gradient(135deg, #74ebd5, #ACB6E5);
  color: #333;
  padding: 0;
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* HEADER */
header {
  text-align: center;
  padding: 50px 20px 30px;
  color: #fff;
  text-shadow: 0 1px 3px rgba(0,0,0,0.3);
}

header h1 {
  font-size: 3em;
  margin-bottom: 10px;
}

header p {
  font-size: 1.2em;
}

/* MAIN */
main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 20px;
}

/* SECCIÓN */
section {
  background-color: rgba(255,255,255,0.95);
  padding: 40px 30px;
  border-radius: 12px;
  max-width: 500px;
  width: 100%;
  box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

/* FORM */
form {
  display: flex;
  flex-direction: column;
}

form label {
  margin-bottom: 5px;
  font-weight: bold;
  color: #2c3e50;
}

form input {
  margin-bottom: 20px;
  padding: 12px 15px;
  font-size: 1em;
  border: 2px solid #ccc;
  border-radius: 8px;
  transition: 0.3s;
}

form input:focus {
  border-color: #3498db;
  outline: none;
  box-shadow: 0 0 8px rgba(52,152,219,0.3);
}

form button {
  padding: 15px;
  font-size: 1.1em;
  background-color: #3498db;
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: 0.3s;
  font-weight: bold;
}

form button:hover {
  background-color: #2980b9;
  transform: translateY(-2px);
}

/* RESULTADO */
#resultado {
  margin-top: 15px;
  font-weight: bold;
  color: green;
  text-align: center;
  font-size: 1.1em;
}

/* FOOTER */
footer {
  text-align: center;
  padding: 20px;
  color: #fff;
  background: rgba(0,0,0,0.1);
  font-size: 0.9em;
}

/* ALERTA FLOTANTE */
#alerta-flotante {
  position: fixed;
  top: 20px;
  right: 20px;
  background-color: #e74c3c;
  color: #fff;
  padding: 15px 20px;
  border-radius: 8px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.25);
  z-index: 1000;
  font-weight: bold;
  display: none;
}

#alerta-flotante.show {
  display: block;
  animation: aparecer 0.4s ease;
}

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