Easy badges; Start off with a few spread proximity mines; unlock all three valves (400 cost) and then start building buzzsaws, starting in the lower right corner and placing them slightly overlapping in a long line. Once the buzzsaw cost is 16K; start upgrading the valves, and you should have the Original Mode badge in 4 minutes.
For unlimited mode; same strategy, finish the line of buzzsaws, and then fill the floor with bouncers for an unlimited combo. Press S to stop once you've reached your desired score.
If the king set out to gather the strongest heroes of the land; why am I left with hiring four lvl1 yahoos who stand shooting at an empty stretch of land in front of the exit sign for five minutes because I didn't specify with enough precision that they had already killed the enemy and should finish the level?
Still; good game; cute little grind-fest with surprising depth. Any.
To make the game auto-fire, hold down left mouse button and move the cursor outside the game screen. Right clicking to bring up a menu while shooting also work.
This allows you to do something else while the game plays itself. Combine this with automatic targeting weapons; one laser on each side of the main cannon and dual seekers on the rest of the weapon slots, and you will be able to play through most of the game without having to pay attention.