Wow, this is seriously impressive for a game made in a week! There's a lot of potential here but it seems like from your comment you knew how where you were taking this concept further. I love the meta item 3d glasses, and the art style is really charming.
I did find that a few of the yellow platforms later in the level wouldn't support the player in 2d mode, maybe missing the 2d colliders? The time limit for the 3d mode felt like more of an inconvenience than a game mechanic but you may have had more planned for it.
I'm really impressed with this, great work! And good for you for getting something together to upload even if it wasn't all you wanted it to be, it's still a very solid game.