Multiple, by 
Eh, what’s there even to say, it’s hard to give a rating or a review or any sort of opinion on this upload, since I don’t even know what it’s supposed to be. I mean yeah, I guess it’s categorised as a “Single Player” upload, but the level doesn’t seem to want to fullfill the list of things required to be called a single player level. You just drop into a (apart from the layout and pointless pickups) completely empty map without any purpose or goal of what you are supposed to be doing. Once you actually start exploring the level you realise it’s just a bunch of warps to different locations with seemingly no good reason. There’s a coin warp that just warps you back to where you came from (also, the gold coins respawn in the exact same room the coin warp is in).
Then you have another room that just gives respawning green gems. It’s one thing to add dozens of warps that progress the level in no particular way, but it’s another to give mostly no good indication of where these warps are. Sure some of them are in door textures but a lot of them are just randomly placed.
Also apart from a Dog I found, there are no enemies in the level, adding even more to the confusion of what this level is intended for. Are walking simulators a thing in platformers too?
The worst thing is that there is actually a complete level (as far as layout is concerned), so this whole thing could be salvaged by making it into a proper single player level, that would at the very least be decent (with sensible item and event placement of course).
I feel bad for giving it such a low rating, but there’s not much to recommend in this, since there’s no real point in playing the level. I don’t even know if it has an actual end or if it’s just a pointless loop inside a goalless level, since I didn’t even see an ending areas with end level triggers, but to be fair I only checked the level in the editor for about 2 minutes.
Maybe you guys can see what I can’t see and understand what this map is supposed to accomplish.