Welcome to Scratch Tower Defense!! Click on a tower to buy, click on the ground to place, then click when the tower is pointing the right way. Click again to upgrade! Press the book in the bottom right to see the guide. The Variable on the left is your lives, the middle is the level, and the right is the amount of money you have. Space to enter/exit the shop.
Credit to ninjakiwi for make the original Bloons TD. Credit to @dzluke for debugging. Will add more soon.