Orcs Must Die! [Steam store page]
While not co-op like the sequel, this game has an excellent sense of humor and decently balanced maps. Too bad the humor didn't carry over to Orcs Must Die! 2

I want to like this game, but while the graphics are gorgeous and the flying feels good, the content is lacking and inconsistent. The difficulty curve is polar opposites most of the time, either you're dominating the enemy or dying very quickly, and there's little to do besides pick up resources and shoot enemies.

The EVERSPACE - Encounters DLC pack sounds like it adds some actual mission content, but I haven't played that so I don't know if it's actually satisfying, and it's silly to be charged extra for what should have been part of the base game. Granted the game+dlc is $40, not $60 like AAA titles, but it also has a lot less content than one too.

I give them credit for the weapon design and feel though - each of the main ones is unique and feels powerful if used correctly. And although there are only three ship types they each play completely differently. It's just too bad they didn't add a decent variety of gameplay to go with them.

Hotline Miami [Steam store page]
Prepare to enjoy smashing open heads with a bat, slitting throats, and shooting enemies at breakneck speed in a psychedelic environment.

Battle Group 2 [Steam store page]
A refreshing change from normal bullet hell games. You can't steer, your only defense is to shoot down the missiles, planes, and boats attacking you.

Furious Angels [Steam store page]
Simple yet elegant gameplay. This is a great example of how to make a game engaging but super accessible.

Simple, but enjoyable. I find the enemies more distracting than fun - but love the collecting aspect of the game. It reminds me of the gameplay from N64 titles like

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Beat Hazard [Steam store page]
An interesting mix of music and gaming - enemies generated by songs. Disappointing that they charge extra for multiplayer (DLC - BH Ultra).

The casting system is reasonably intuitive, and the gameplay itself is as fun as Torchlight, though the heavy corridor feel of the levels detracts a bit. There is a smattering of story and humor throughout, but I wouldn't call it story-driven.

Steel Storm: Burning Retribution [Steam store page]
A nice twist on the classic arcade top-down shooter. Similar mechanics of power-ups, but with complicated maps, mission objectives, and the ability to move in any direction. This is retro done right - worth playing.

Fairly fun indie game, though I wish the Princess Rush game mode didn't allow players to steal from each other - it changes the tone a bit. Aside from that it's a surprisingly difficult, yet enjoyable play. Does suffer from some crashing issues.

Revenge of the Titans [Steam store page]
A tower defence game that keeps you on your toes. There are tons of upgrades and not enough time to buy all of them - you definitely won't get through all the levels on the first try.