I really enjoyed the game. The levels are nicely designed. I liked the three different biomes.
Others have already suggested these, but I'll write them anyway.
The "Tank controls" control system is a bit old-fashioned. A more modern TPS control would be better, where you can use a mouse or joystick to set the direction.
In terms of replayability, the spawn points of the pickable items could be located in more places, and they are randomly selected when each level loads.
All in all, this is an excellent job!