ok 2 things i found f* up about this game 1. at firsti kept restarting causei died instantly :P until i missed it and went on to find out you have to buy the first upgrade to play. 2. for boss its not how many hits its just last 4 rounds and you win :P btw secret passage on << of spawn and multiplier should be maxed first
beat in 9 as well took me 8 to max everything btw speed + power both max = gg :P i beat the first 3 bosses before they started to attack ... and for the rest i just used max speed and strifed..