The worst part of all this work is when it isn't clear what to do next. Product Owners don't get enough appreciation.
Next up to bat: the turret powerup. This powerup is pretty simple: select it, and a random-color turret will be placed in front of the cube to defend it. It's great because in levels with more than 1 color, it will allow you to ignore all traps of that color and focus on the other ones.
This is not a fully fleshed out mechanic yet, as there is no way to purchase more for use in levels. So that part will be next!
It seems that now would be a good time to start putting this game in people's hands to see what they like or don't like. I've been looking through the r/unity2d subreddit a lot and I'll likely post stuff there first.