* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  text-decoration: none;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

:root {
  --primary: #00a5b8;
  --primary-dark: #008694;
  --accent: #667eea;
  --accent2: #764ba2;
  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --shadow-strong: 0 15px 40px rgba(102, 126, 234, 0.35);
}

body {
  background: linear-gradient(135deg, #e0e5ec 0%, #a8b5c8 100%);
  background-attachment: fixed;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

main {
  width: 100%;
  max-width: 900px;
  margin: auto;
}

.contenedor_todo {
  width: 100%;
  margin: auto;
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 30px;
}

/* Caja trasera con botones */
.caja_trasera {
  width: 100%;
  padding: 40px 30px;
  display: flex;
  justify-content: space-around;
  flex-wrap: wrap;
  gap: 40px;
  backdrop-filter: blur(20px);
  background: linear-gradient(
    135deg,
    rgba(0, 165, 184, 0.85) 0%,
    rgba(0, 188, 212, 0.75) 100%
  );
  border-radius: var(--radius-lg);
  box-shadow: 0 10px 35px rgba(0, 0, 0, 0.3);
  border: 3px solid rgba(255, 255, 255, 0.3);
}

.caja_trasera div {
  color: white;
  text-align: center;
  flex: 1;
  min-width: 250px;
}

.caja_trasera div p {
  margin-top: 18px;
  font-size: 16px;
  line-height: 1.5;
  opacity: 0.95;
}

.caja_trasera div h1 {
  font-weight: 700;
  font-size: 28px;
  text-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
  margin-bottom: 5px;
}

.caja_trasera button {
  margin-top: 25px;
  padding: 12px 35px;
  border: 3px solid white;
  background: transparent;
  font-size: 15px;
  font-weight: 700;
  cursor: pointer;
  color: white;
  border-radius: var(--radius-md);
  transition: all 0.3s ease;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  box-shadow: 0 4px 15px rgba(255, 255, 255, 0.2);
}

.caja_trasera button:hover {
  background: white;
  color: var(--primary);
  transform: translateY(-3px);
  box-shadow: 0 8px 25px rgba(255, 255, 255, 0.4);
}

.caja_trasera button:active {
  transform: translateY(-1px);
}

/* Formularios */
.contenedor_login-registro {
  display: flex;
  flex-direction: column;
  gap: 30px;
  width: 100%;
  max-width: 500px;
  margin: auto;
}

.contenedor_login-registro form {
  width: 100%;
  padding: 45px 40px;
  background: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(12px);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-strong);
  border: 3px solid rgba(0, 188, 212, 0.3);
  display: none;
  position: relative;
  overflow: hidden;
}

.contenedor_login-registro form::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 5px;
  background: linear-gradient(
    90deg,
    var(--primary) 0%,
    var(--accent) 50%,
    var(--accent2) 100%
  );
}

.formulario_login {
  display: block;
}

.contenedor_login-registro form h2 {
  font-size: 30px;
  text-align: center;
  margin-bottom: 30px;
  color: var(--primary);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  text-shadow: 0 2px 4px rgba(0, 188, 212, 0.15);
}

.contenedor_login-registro form input,
.contenedor_login-registro form select {
  width: 100%;
  margin-top: 18px;
  padding: 14px 18px;
  border: 2px solid rgba(0, 188, 212, 0.25);
  background: #f8f9fa;
  font-size: 15px;
  border-radius: var(--radius-sm);
  outline: none;
  transition: all 0.3s ease;
  color: #333;
}

.contenedor_login-registro form input:focus,
.contenedor_login-registro form select:focus {
  border-color: var(--primary);
  background: white;
  box-shadow: 0 0 0 3px rgba(0, 188, 212, 0.12);
}

.contenedor_login-registro form input::placeholder {
  color: #999;
}

.contenedor_login-registro form select {
  cursor: pointer;
  color: #666;
}

.contenedor_login-registro form select option {
  padding: 10px;
}

.contenedor_login-registro form button {
  width: 100%;
  margin-top: 35px;
  padding: 15px;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent2) 100%);
  color: white;
  font-size: 16px;
  font-weight: 700;
  border: 2px solid var(--primary);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.3s ease;
  text-transform: uppercase;
  letter-spacing: 1px;
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.4);
}

.contenedor_login-registro form button:hover {
  transform: translateY(-3px);
  box-shadow: 0 10px 30px rgba(102, 126, 234, 0.5);
}

.contenedor_login-registro form button:active {
  transform: translateY(-1px);
}

/* Responsive */
@media screen and (max-width: 768px) {
  body {
    padding: 15px;
  }

  .caja_trasera {
    padding: 30px 20px;
    gap: 30px;
  }

  .caja_trasera div h1 {
    font-size: 24px;
  }

  .caja_trasera div p {
    font-size: 14px;
  }

  .caja_trasera button {
    padding: 10px 25px;
    font-size: 14px;
  }

  .contenedor_login-registro {
    width: 100%;
  }

  .contenedor_login-registro form {
    padding: 35px 25px;
  }

  .contenedor_login-registro form h2 {
    font-size: 24px;
  }

  .contenedor_login-registro form input,
  .contenedor_login-registro form select,
  .contenedor_login-registro form button {
    font-size: 14px;
  }
}

@media screen and (max-width: 480px) {
  .caja_trasera {
    padding: 25px 15px;
  }

  .caja_trasera div {
    min-width: 100%;
  }

  .contenedor_login-registro form {
    padding: 30px 20px;
  }
}