very good, but improveable
i loved the gameplay and style of the defensegame. its simply fun producing robots over and over to fight other robots. well done.
so, my 8stars rating doesn't result, because i liked this game so much, because otherwise it would be 10, but as many others said already its getting boring after some time.
endurance is a nice idea, but far too easy. i am at 2000 sec now and the enemy has absolutely no chance to get better.
overall i think you could improve this brilliant game and put in some effort. it is worth the time. definitely.