Custom CSS is the best option. Your code is almost correct, the ‘.asp_content’ is the class name. However instead of ‘display:none’ changing the text color to transparent is the way to go, as otherwise it will hide the whole result.
@media only screen and (max-width: 480px) {
.asp_content {
color: rgba(0, 0, 0, 0) !important;
}
}