For this step you should create four waypoints, starting at 10% and incrementing by 10% for each of the following waypoints.
The syntax should look something like this:
@keyframes wave {
value {
//rule here
}
value {
// rule here
}
... etc ...
}
Note that you are not specifying any animation rules yet, just creating empty waypoints at those values. You can leave the sets of curly brackets empty for now.