Wait? White Noise Online came to Steam? I haven't played it Steam-wise yet (plan to pick it up), but here are some impressions from the Xbox Live version:
White Noise Online is a first-person multiplayer survival-horror game that's a clone and spun-off from the Slender-style of games. The game originally released as two Xbox Live Indie games (one for multiplayer, one for single player), and has seen a lot of updates and additions since its release (the Steam version is based off the last big update they did for the game earlier this year).
In White Noise, either you or you and three other people go to various locations to collect radios. There's a slight narrative going on in each level, as each radio sends out a transmission, and in the single player mode (which, while this is called White Noise Online, seems to have been added to the game from the single-player version of the game) you follow a cutscene narrative between stages. It's a nice thought, but honestly the game is a lot more about the multiplayer.
To basically describe White Day would be in simple, "If Slender and Scooby-Doo crossed over." That sounds like a weird thing to say, but it mainly has to do with the characters. They look cartoony, while they collect radios their goals are basically mystery solvers looking for clues (with some ridiculous character bios), and you can play as everyone from a nerdy schoolgirl to an Elvis look-alike. Each character has different stats though, areas where they're weaker and stronger in. For example, some characters can sprint longer, some characters can stand being alone much better (if you stray too far, your sanity starts to deplete before you start having a panic attack), some characters recover from panic attacks quicker, some have more health, some can look at the monster longer and lose less health, some can hear radios louder than other characters, and so on. There's quite a few characters, and there's a pretty fun and rewarding unlock system to get them (notably, all the characters from the previous Xbox Live release that could only be unlocked by owning other games are now regularly unlockable).
As a Slender clone, the gameplay is simple. You walk around, can turn your flashlight on or off (it has batteries that need to recharge), and collect radios (which emit a sound). A monster is chasing you, who will slowly drive you to either panic, try to separate you from friends, or kill you. He teleports around and gets tougher as you get more radios. There's a lot of small twists that come to the formula, but if you've played Slender you know the sort of thing to expect. In Multiplayer you play as the four survivors, no playing as the monster here. Probably my two favorite features multiplayer-wise is the death mode and the results screen. When you die in White Noise Online, you come back as a ghost that the living (and dead) players can see. As a ghost, you can see the whole level brightly lit-up, and can move a lot faster. But of course, you can't interact with anything, and you also can't see the monster. However, you can either scout out for radios, stick with the living players (they'll go insane and into panic mode with no one around them, and apparently a ghost counts as someone), or just relax and explore the level freely. It's a nice touch that makes players still active even after they die. The results screen also provides an amusing map of the level you just did and shows the route that everyone took when they played, where they died, and statistics like how many radios each player picked up, how many times they were attacked by the monster, went into panic mode, the total distance each person walks, survival time, and so on.
The gameplay has difficulties, that mainly change some things about the monster and how many radios there are to pick-up. Doing well in certain stages on certain difficulties unlocks you more things in the game (such as beating a stage on a difficulty, collecting a certain number of radios in the stage, and so on).
I also can add that the stages are very fun and varied. Basically there's three types of stages, and then alterations based on these. There's stages that are big and open, with only certain landmarks to guide you. There's levels in enclosed spaces, with lots of tight corridors and twisting rooms, and there's 'island' stages, where there's multiple areas that you can only reach by certain limited access points, separating parts of the map into different 'islands'. The themes of the stages range from a tropical island, to a snowy forest, to a museum, to a government base, and more. They're all pretty fun.
Overall I'd actually say this game is superior to most other Slender games. The online is well thought-out, fun, and still manages to be scary and tense despite the fact you're playing with other people. That and being able to play with friends in a game like this is a lot of fun. The new mechanics add some interesting twists to survival, and the sort of friendly co-op and also competitiveness to do better than your friends aids to some interesting scenarios. The devs note that if it does well they plan to continue further support in the future for new updates, stages, and characters, so if a multiplayer Slender-type game sounds interesting to you, this is it.