Collect sun by hovering the mouse over it. Spend sun to grow plants, don't let the zombies reach the house.
Made this in, probably a total of 6-7 hours (Not including time in between working on it) As a test to see what it would be like to make PvZ in scratch, specifically a version that's intended to be easier to mod. Seems pretty good, planning on starting a tutorial series on how to do this in April.