#as-izq {  
  display: block;
}

#menu-t {
  display: none;
}

#menu-toggle {
  display: none;
  /* hide the checkbox */
}

@media all and (max-width: 700px) and (min-width: 0px) {

  #menu-t {
    display: block;
    height: 50px;
    width: 50px;
    line-height: 50px;
    text-align: center;
    color: white;
    font-size: 150%;
    background-color: #83CE69;
    cursor: pointer;
  }

  #as-izq #nav {
    display: none;
  }
  
  #menu-toggle:checked+#nav {
    display: block;
  }

  #as-izq label:active #nav {
    display: none;
  }
}