Hi, thanks for the comment!
Like many other things, the turret looks (and the ability to easily distinguish them) fell victim to the time limit of the jam. I have a few ideas how to fix that, if I find the time to work on this one a bit more. For example, I wanted to give each turret a UI visible only when you hover your mouse over that turret. It would show the turret HP (like it does in the top right corner right now, with an additional progress bar), its state and it would display the turret range. The turret range is actually programmed in, I just didn't have enough time to fix up the rest, so I hid it.
As for the different sprites for the turrets - my original idea was to have separate sprite for each turret and for every state of that turret (almost dead, heavily damaged, lightly damaged and fully functional), but again, didn't manage to do it in time. I want to create a larger map with a bigger (and expanding as the game progresses) area to defend, so I will have to make those turrets easily distinguishable. When I take a break from the weekly jam I'll try out some ideas.
Thank you again for the comment! Also, I played a little of your game (Hyperdrive Repair) earlier, but I want to spend a bit more time on it before commenting. For now I can only say I like it. :)