Okay so... if you max everything out and hold left or right it gets kinda impossible to lose... my dude has been surfing at like 18k feet for the last 20 minutes and hasn't died yet.
Trick for the medium badge: Use the large dungeon map. Kill enemies at the bottom of the level and when you're low on health, head to the farthest right on the bottom and jump up into the little alcove on the left (the alcove spawns ammo, too). Few enemies can reach you there, so you should be able to regenerate hp. Once full hp, jump back to the bottom and kill enemies until your hp runs low, and repeat. As always, upgrade your weapons from the starting ones by pressing and then collecting enemy drop weapons for best effect. + if you like
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