That concludes this tutorial. But there are still many more things you can do with this game.
First of all, you can play endlessly with the variables to create a different game challenge, change the number of enemy waves, change the number of enemies in the game, or how they behave. You can change and test building funds to find the perfect difficulty level.
You can improve the graphics by adding more color and texture to the sprites. You could draw creepy faces on the enemies to make them look more like creatures.
And then, you could also add more levels in the game, change the background, and relocate the platforms and the base. Of course you have to achieve this with scripts since each level requires an update of placements ...