Textures are good mix but i feel like texture for surf could be improve, it looks like you sliding on a carpet. I like the way you used pillars, it make looks less empty. Water looks bad, you should use maybe something less cheap. It feels like we are in a cave with dx60. Some colors not too bright would be maybe cool and make the ambient less dull. Idk for the glass into surf too, it just doesn't fit.
- Details -
There are not really. Except for ivy. You could use trees or a good skybox with windows. It would improve lights and make everything better with shadows and sunlights.
- Lights -
Used default white no ? Maybe some props with yellow / Orange lightning could improve the esthetic Even for sun, try put bigger skybox with more sunlights with orange or yellow, it will be great with some shadows and some brightness.
- Difficulty -
I will talk about the main map first. It's hard map and a bit nervous sometimes. It's short stage and that's great but most of time you finish the stage tilted cause you spammed so much time and not much skill into. Like it's not about skill rewarding but more time rewarding, time you spent on.
Bonus are great but this b1 tho, all about luck. On Ksf we spammed like hell yea 100 times and somes can't just end it because it's too hard. b4 is really great, original and the difficulty is perfect.
- Misc -
It feels like sometimes you want people nervous ending stage with not many speed so when they don't reach they just fall like shit. It's ur way to map but it could be improve by making stage bit longer and make end less lucky.
The logo you created is really great, maybe put some into your stages.
More different ramps will make variant levels.
You can use some particles or sprite, even decals to make map more personnal and attractive. Here, it's bit neutral and when you look at it, you dont really want to play it.
To resume, i think it's a great map but i think you could improve on spending time more longer to make ur maps.