First three levels are self explanatory.
For the last level, the developer was kind enough to help me out as I couldn't figure it out on my own.
The requirements for beating this level are hitting all of the targets in the level. (technically one doesn't count but it's easy enough to get that you'd waste more time trying to avoid it)
He said,
"There are 11 targets (though, there's a small issue where 1 of them doesn't count toward completion).
There are 3 targets in the middle of the street. The next 7 targets are located in the driveways of each house.
There is 1 target that's a bit harder to find. When you get close to the pink house, at the end of the court, the garage door opens. Inside the garage you'll find a target.
The orange target, located near the orange house (behind where the player starts), doesn't count toward the 10 targets needed to win.
Thanks for playing!"
The tough one that I couldn't find, was as he said, in the garage of the pink house. Take the ball and stand in the driveway, and the garage door should open.