Things that have been added:

Saving mode:
There has been added a new option in the menu, it is called "Continue". It does so when you have played and close the game, you then don't have to completely restart (the wave that you were on will get restarted), you just press the "Continue" option instead of the "Start" to continue where you were :)

Death Effect:
When you kill an enemy, the enemy will then turn white and the transparency of the enemy will then go down until it completely disappears and then it gets destroyed.

New Controls:
ESC - Close game
E - Open shop