I made it to 5th wave... very fun game...
2 suggestions... change the colour of the pink enemies (the first ones) because after you have (literally) painted the floor with a few of them they are somewhat difficult to distinguish... it was not so much a problem with blue and green ones... And at the end of my first playthrough i lost because some had entered the center and i could see i had 3 enemies remaining but i could not see them and i didnt know that they were inside...