Upgrade skills, spam destroyers, watch your computer slow to a crawl, win.
I like this style of game, but they always seem to degenerate into "spam your best ship as fast as possible until your computer dies". In this case, your best ship being the destroyer (LOL@Hindenburg, went down faster than an enemy cruiser to the flak cannons)
Hint: More sprites isn't always better. Fighting a big blob of faceless mobs, by firing a huge blob of arrows out of a gatling gun, is a great way to freeze up my computer, but not terribly fun.
Cannon Operation is:
1: Drop ball into cannon
2: Cannon fires
There's one level where it's more complicated than that, in which you have to essentially block the cannon's firing with a second ball.
For those having problems with 31:
1: Put one bar with the left end barely on the Lowest support, and the right end barely on the right support.
2: Put the second bar with its left end on the leftmost support, and the right end on the first bar.
 "Short Circuit"){kind=icon}
 "Universal Nano Counter Force"){kind=icon}
 "2039 Ryder"){kind=icon}
 "Battalion: Skirmish"){kind=icon}
 "Meeblings 2"){kind=icon}
 "Seed of Destruction"){kind=icon}
 "LEGEND OF PINGPONG"){kind=icon}
 "SWING CAT"){kind=icon}
 "Learn to Fly"){kind=icon}
 "Black Navy War"){kind=icon}
 "Medieval Rampage"){kind=icon}
 "Avoider Extreme"){kind=icon}
 "I Love Traffic"){kind=icon}
 "Factory Redux"){kind=icon}
 "Five Minutes to Kill (Yourself)"){kind=icon}
 "The Unfortunate Necromancer"){kind=icon}
 "Civiballs"){kind=icon}
 "Assembler 3"){kind=icon}
 "Mirrors Edge 2d"){kind=icon}
 "Paradoxon //the flash game"){kind=icon}