Really fun. Only thing I can say is to add music and to reduce the Armor the Splitter has, since they take forever to kill unless armor piercing is on a gun and even then it still takes a bit. Made it to level 10 before stopping.
Splitter has 0 armour, though?
The enemies that split into multiple enemies aka the third enemy shown, when introduced they said they have armor.
They have 0 armour.
Whatever it was, they have more HP than anything else and it takes a long time to kill each one.
Upgrade you gun and it will become easier.