Single player, by 
Uhh… What?
Also, you might want to release all the levels of an episode in one pack. Anyway, onto the review.
“Nakari Forest Winter” is a single level that is apparently part of an episode (according to the level name, the second episode of whatever series this is a part of). The tileset that comes with the level is (as far as I know) rarely used, and it doesn’t look that bad for a Diamondus conversion.
The level itself, while fairly large, is extremely dull. While the level is mostly linear, it somehow manages to accomplish a feeling of “what the hell am I doing?”, mostly because the level is at some points impossible (not in the good sense, it is literally impossible to pass through some points in the level without using jjnowall). The level feels as if no beta-testing was done on it, and while space is used efficiently and it pulls off somewhat unused ideas (a switch to turn on and off tiles, as well as bringing back the frog concept), for the most part the level feels uninspired.
The eyecandy is subpar, a few gem ground tiles thrown here and there among a vast sea of the same ground tile everywhere. There are quite a few tile bugs throughout the level, and the level makes no use of background eyecandy. The textured background’s fade is set to black, there were no birds singing, the pants were dead, and the ground was messy and bloody from headcrabs.
While the level design is mostly unappealing and the eyecandy isn’t interesting, the level manages to show some interesting ideas. I won’t recommend downloading this, though.