Fun stuff! Reminds me of some of the early days of addictinggames and armorgames. There were some really fun games with drawn-on-paper style visuals.
I do think it could benefit from a better overview of the controls. I figured out how to place cannons after a bit, but the buttons on right-click are too small to read, so I was just guessing what each one did. I also ran into some issues with cannons carrying over after restarts. But a fun game nonetheless.