:root {
  --color-primario: #1d4ed8;
  --color-primario-hover: #1e40af;
  --color-fondo: #f1f5f9;
  --color-texto: #1e293b;
  --color-error: #b91c1c;
  --color-error-fondo: #fef2f2;
  --color-exito: #15803d;
  --color-exito-fondo: #f0fdf4;
  --color-borde: #cbd5e1;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: linear-gradient(135deg, #0f172a, #1d4ed8);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  color: var(--color-texto);
}

.tarjeta {
  background: #ffffff;
  border-radius: 12px;
  padding: 40px;
  width: 100%;
  max-width: 420px;
  box-shadow: 0 20px 45px rgba(15, 23, 42, 0.35);
}

.marca {
  text-align: center;
  margin-bottom: 8px;
}

.marca h1 {
  margin: 0;
  font-size: 28px;
  letter-spacing: 1px;
  color: var(--color-primario);
}

.subtitulo {
  text-align: center;
  color: #64748b;
  margin-bottom: 28px;
  font-size: 14px;
}

.campo {
  margin-bottom: 18px;
}

.campo label {
  display: block;
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 6px;
}

.campo input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--color-borde);
  border-radius: 8px;
  font-size: 15px;
  transition: border-color 0.15s ease;
}

.campo input:focus {
  outline: none;
  border-color: var(--color-primario);
}

.mensaje-campo {
  display: block;
  min-height: 18px;
  font-size: 12.5px;
  color: var(--color-error);
  margin-top: 4px;
}

.btn-principal {
  width: 100%;
  padding: 12px;
  border: none;
  border-radius: 8px;
  background: var(--color-primario);
  color: #ffffff;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s ease;
}

.btn-principal:hover {
  background: var(--color-primario-hover);
}

.btn-principal:disabled {
  opacity: 0.7;
  cursor: not-allowed;
}

.enlace-secundario {
  text-align: center;
  margin-top: 20px;
  font-size: 14px;
}

.enlace-secundario a {
  color: var(--color-primario);
  text-decoration: none;
  font-weight: 600;
}

.enlace-secundario a:hover {
  text-decoration: underline;
}

.alerta {
  display: none;
  padding: 12px 14px;
  border-radius: 8px;
  font-size: 14px;
  margin-bottom: 18px;
}

.alerta.visible {
  display: block;
}

.alerta.error {
  background: var(--color-error-fondo);
  color: var(--color-error);
  border: 1px solid #fecaca;
}

.alerta.exito {
  background: var(--color-exito-fondo);
  color: var(--color-exito);
  border: 1px solid #bbf7d0;
}

.panel-bienvenida {
  text-align: center;
}

.panel-bienvenida h1 {
  color: var(--color-primario);
  margin-bottom: 6px;
}

.panel-bienvenida p {
  color: #475569;
  margin-bottom: 28px;
}

.btn-secundario {
  padding: 10px 18px;
  border-radius: 8px;
  border: 1px solid var(--color-borde);
  background: #ffffff;
  color: var(--color-texto);
  cursor: pointer;
  font-size: 14px;
}

.btn-secundario:hover {
  background: #f8fafc;
}

@media (max-width: 480px) {
  .tarjeta {
    padding: 28px 20px;
  }
}