By looking at the repository, I can see only code change is Added a OnCollisionEnter2D function on Both Player1 and Player2 cs files and changed the Update to Fixed Update. Also you have added PowerupSpawner.cs file which is just doing SpawnPower initiation and added a bunch of .png files. If that is the only thing you have done or am I missing anything?
On the coding part the new things on this commit are the buttons functions for the game menu, the FixedUpdate() change where I tryed different ways from the internet to solve the bug but in the end I only needed to change the function's name and the powerup spawner.
On the Unity3D part I had to add each tile manually on the map (and there aren't just a few, I'll add screenshot below, it took me some time to get them as close as possbile to each other and make them look alligned), and after that to test moving between all of them to see where the tank gets stuck and it shouldn't so I moved the tiles left/right/up/down to make a drivable way.
The only big part for coding left is the powerups what each one will do and later on the survival mode, as for the other part the thing that will take me a lot of time is to create each map, place tiles in each one different ways, different places for the powerups spawn.