Balance: It's a small size mirrored map so there is no actual problem with the balance.
Design: The design is the most interesting part of this map. It is similar to Lego maps especially in some spots. It looks like walls are made out of colorful bricks and this makes the map funny and surely not boring.
Detail: I feel like the map lacks some thing. The floor is way too flat and plain. You could have tried making custom decals like splatters of color. Those splatters could be red or blue and used on the floor to break the monotony of yellow. You could also try turning the floor into a displacement and add water here and there. You could use a custom water material where the water's colored red or blue. It would look cool.
Looks: Now here is the problem. If it wasn't for this, I would give the map a rating above 9/10. The problem is that it is way too bright and it really hurt my eyes (It really did when I first loaded it). You need to reduce the max exposure of HDR with an env_tonemapcontroller. You will also need a logic_auto in order to get the first entity to work.
Notes: Nice map but please, reduce the map's brightness. Good job.