To quote Zubon's insightful comment:
"Adventure level 4 is horrible. First there is the design decision to put successive keys at opposite ends of the map. Then you must be level 6 to exit, but there is not enough xp in the adventure game to be level 6 by the end of the 4th map. You must repeat the map several times or play the arcade mode. That is worth mentioning before sending someone back and forth across that map."
Needs a "next wave" button, the machine gun glitch is game-breaking, and needs a save option.
This game could have been awesome, but, as it is, just feels lame and unfinished. It's a shame, because I really love Weasel's games.