@mixin respond-to ($device) {
@if $device == mobile {
@media (max-width: 768px) { @content; }
}
@else if $device == tablet {
@media (min-width: 768px) { @content; }
}
@else if $device == desktop {
@media (min-width: 1024px) { @content; }
}
@else if $device == hd {
@media (min-width: 1200px) { @content; }
}
}