Hey! Well done!
I played for abt 2h ^^.
I leveled everything up to the point where I can simply wipe out the whole map and it was a fun journey. Should there be an end? If so, I fear I missed something. But this was really some new touch to the genre.
I loved the progression! In the beginning I thought: Where are my bullets? But then, after some rounds of upgrades it was easier to kill more enemies and get more bullets. From there it went straight on ^^. I died just once! And I was shocked to see my crystals are gone ^^. Never happened again.
The weapons are nice, too although I played foremost the handgun, the ice gun and the boom stick. The others were nice too but i had enough ammo to wipe out the map alone with the ice gun in the end. The flame gun was okay, but since the ice gun does good damage AND freezes opponents it was the weapon of choice.
The level design is really nice and the different spots to camp are well spread. At first I wondered how to open the bunkers but then it was clear. I would have longed for some destruction of the trees tho ^^.
Music and sounds are nice, enemy variety is absolutely enough for such a small game and seeing mechs was a nice surprise :).
I only would have wished for the final fight to kill the killer of my dad. Maybe its in there and i missed it. If so, please give me a hint.
Definitely a well made game and more than I expect from a game jam.
Good job!
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Ah one more thing: There is a collider missing in the cavern so one can enter the "twilight zone" ... ;) 
