Click to place troops Hold E + click to place troops super quickly. Hold Spacebar to delete troops. Currently there is only Playground mode, where you can set up 2 armies and watch them fight. I am planning on expanding this into a game where you unlock new troops by battling enemy armies, but I'm not sure I'll ever do that.
One thing to know: Scratch has a clone limit of 300, which means you can't place more than 300 troops. This also means that if you do place 300 troops, ranged troops won't be able to throw projectiles, because the projectiles are also clones...