Best time: 37:30
Pretty interesting game, but I do have a few issues with it.
1. The shielded enemies are overpowered. I don't know the exact mechanics of the game well enough to explain why, as this issue only really becomes apparent due to the issue I'm about to name.
2. The enemy spawning is REALLY weird. For the entire time I was playing endless mode, the bottom two rows would ONLY spawn the shield enemies. I had to focus ALL of my firepower on said bottom two rows, because replacing even one of the lasers with a gatling gun or lab would've ruined everything. This is even with the upper 4 rows containing gatling guns almost exclusively, upgraded with scattershot to be able to help with the bottom two rows. I pretty much never saw any enemies come from any row besides the bottom two, which is what leads me to feel they're overpowered. Although this might not even be noticeable if enemy spawns were even instead of weirdly focused.
3. Feels too reliant on RNG. I had several games at the start where I had twice as many labs as I did actual weapons. It doesn't help that the shock weapon seems totally useless, meaning it's a coin flip whether a tower you get is actually useful. And in some games, I only got one column on a given row, and literally had no way to defend it, as there was no room to place a second gun.
4. Upgrading via the labs is VERY tedious. Just nonstop clicking. And you get to a point where each individual damage upgrade matters so little you don't even know why you continue to bother clicking on them. The only reason I even lost when I did was because I got bored and decided to just sit and watch the outcome. Surprise surprise, it was the shield enemies that did me in.
Potential fix for #4: Make it possible to buy lab upgrades in bulk. Maybe if multiple labs are ready to provide an upgrade, choosing an infinitely-stackable upgrade causes ALL labs to provide that upgrade, and go on cooldown. I feel this would make it a lot less tedious, but this is just one idea for how it might be fixed.
All in all, interesting concept and I'm glad I checked it out, but I probably won't be trying to get a better time.