This feels much more satisfying and well-tuned than the original Sanctum - and the addition of co-op takes it to a whole new difficulty level.

Orcs Must Die! 2 [Steam store page]
They added co-op, but lost some of the humor that made Orcs Must Die! so fun. Similar gameplay, with more expansive levels to challenge two players.

Saints Row IV [Steam store page]
While Saints Row: The Third was fun madness, this sequel adds a superhero twist with great new abilities and much easier travel than the previous game.

Trine 2: Complete Story [Steam store page]
I didn't enjoy this nearly as much as Trine - it felt like less of a puzzle game and a lot more platformer. The wizard's triangle is gone, and all the characters swim the same now.

PAYDAY The Heist [Steam store page]
A fun co-op experience. The latest AI patch made it much easier to play without all four players being human. Enemy AI still has nearly perfect aim, but the body armor balances nicely if you use cover. You earn new guns and upgrades as you play.

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.

Left 4 Dead 2 [Steam store page]
Even though Killing Floor doesn't have a story line I still prefer it for co-op fun. This is incredibly easy, and the scripted way the special zombies pop out next to you is annoying unless you have the maps memorized.

Killing Floor [Steam store page]
The graphics are a bit rough but this game is all about speed and accuracy killing waves of experimental creatures. Forget story, the co-op is loads of fun with a group of friends, and fairly challenging as well.

The most difficult part is the way enemies rubberband - if you run full tilt on many maps, and turn around they'll still be very close behind you - rounding the nearest corner or doorway. The spawn locations also don't seem to be set specifically - they seem to appear directly around any corner that you haven't looked around in the last few seconds, or further ahead if you're running rather than camping. On some areas in maps they also drop down from above, off buildings or through holes in the roof.

These mechanics aren't necessarily flaws - they make the game much more fast paced and difficult than it would be if you could kite them more strategically. Kiting is still very much possible because the game limits the number of enemies on the map at any time - so if you can group them all behind you then they will slowly appear in front of you as you kill ones behind.

Expansive levels that make Portal look like a tech demo, with quite a few new fun mechanics and a lot of back-story about the Aperture Corporation. It's about three times as long as the original, and once again ends with fantastic music.

An interesting blend of FPS and tower defense. Seems geared toward multiplayer, and probably fun in that aspect. Novel controls - easy once they're familiar. Flaw with anti-aircraft guns - they all shoot at the same target, needs better AI for that.

Team Fortress 2 [Steam store page]
I wanted to love this game, but found it hard to get into because it requires team effort (mainly a healer at your back) or you die exceptionally fast. Unlike Unreal Tournament or Counter-Strike: Source where you can easily play a quick lone wolf match

Spiral Knights [Steam store page]
The graphics are cute and the game seems potentially fun, but it lags incredibly bad on my PC - and I'm not sure if it's a problem with the game itself or their servers coping with the player load. Regardless, unplayably laggy even when moving.

Minecraft in 2D, but with good combat and bosses. You can make a large variety of weapons and potions, and there are sky islands, dungeons, and the underworld to explore. The 1.1 update adds tons of content and improves the game considerably.

A truly great puzzle platformer! Fun yet relaxing, this game has good graphics and three different characters - each with unique abilities. You can switch characters at any time using number keys, using their abilities to progress through the level

Borderlands [Steam store page]
This is a weird mix of MMO leveling and FPS, and in a certain aspect it works okay, but at other times it can be frustrating.

The beginning of this game includes a lot of scripted sequences, which can be a bit annoying if you play through multiple times, as was intended (you reach level 35 or so on the first playthrough, 50+ on the second). The first time playing it seems incredibly smooth and well paced, teaching you all your necessary skills painlessly.

The game itself isn't hard - I was level 13 before I died the first time - but after a while it gets annoying to take headshots and not actually kill the enemy, like a normal FPS. This is due to the level mechanic - killing an enemy one level above you is difficult, and two is nearly impossible. The exception is playing the tank/melee character, who has a special ability that flattens higher levels with ease.

There is also a melee enemy class known as Psycho that has an annoying tendency, when injured, to run full tilt at you holding a hand grenade above their heads. Many times when this happens they are inescapably close, which results in your instant death.

Lastly, the bosses tend to take 3-10 minutes for a solo player to slowly tear through their massive health pools - almost like fighting an MMO raid boss on your own. Almost every boss also has a group of annoying normal enemies to dispatch during the beginning of the fight as well. These encounters are probably much more suited to the co-op gameplay.

Overall a mixed bag, fun in certain aspects, but also one of the few games that makes me feel angry when I play it. That's a sure sign the enemies aren't quite as balanced as they should be.