Very fun but could use some upgrades.
To be honest I spent a lot of time in the sandbox and I have a suggestion if you ever plan on making an update or newer version. Saving cell structures for easy pasting on the grind. Kind of like a stamp so you don't have to click and drag as much. Maybe even toss in a rotation option. Don't know how difficult that would be to put in but maybe even a inverting option. Too be honest I wanted to fill the whole grid but I just have it in me to trace that whole grid. I know most of this is sandbox, hell maybe all, but this game leaves a lot of room for experimenting and it doesn't get stale quick.