uhhhhh I found a glitch i was playing episode one level one or whatever and the game froze, my score shooting up to somewhere along the lines of 99999999999999999999999999 and combo at 10k and each shooting up faster and faster.
=D I figured out a good combo builder just get the laser gun in the ranged weapons shop and just hold Z because this has an extremely high fire rate. However, if you are a higher level, you can hold X for one long continuous ray of lasers and all you need to do is just get it's attack upgraded and it's an undefeatable weapon.
I found a pretty good pwnage trick for newbs: get 10k pixels and buy laser gun in shop and use quick fire and you get a beam of lasers instead of small shots.