Medium mode is too easy, but when i start extreme mode and get around the 110th wave the waves just seem impossible. the first time I did extreme I got a little space bar happy, but even when i didn't the waves seemed impossible around the 110th. even the ICBM type missile combo didn't do that much damage
 "Achievement Unlocked"){kind=icon}
 "Hedgehog Launch"){kind=icon}
 "Onslaught2"){kind=icon}