Trigger, by indie developer increpare is a side scrolling shooter with simple graphics, but targeted to addicted gamers looking for a challenge on the genre.
The following video is a speedrun, so spoilers etc… (if you plan to play it through, watch some bits of it just to know what you’ll face):

The gameplay is pretty simple too. Your ship has a weapon that allows you to lock on to multiple targets, and then shoot them directly.
Fun for hardcore side scrolling gamers, lots of frustration for normal gamers…
The game is free, you can get it at Increpare’s official Trigger website.

Source: IndieGames