Secret Unlimited Health Glitch
I just found out a glitch in this game. It is from a little error within the actionscript. So here it is: (PS, I only did it in Survival Mode, I don't know if it will work on the others)
Get your HP down to 10 at the most. Once youve done that get a landmine. Plant it right under you and detonate as soon as possible before the reds attack you. If it is sucessful, Your hp will now be in the minus's. And it will keep going down and you will never die.