Last room is quite good, before that, nah not so much. especially tight timing even though it is doable. Solution to it:

1. Laser room is very simple for experienced players. The pre-hit pylon is a clue, the game is linear and you are not coming back to it.
2. Non-cardinal angle redir the laser to hit two more pylons while end at wall.
3. Portal the angled laser to final target, walk.
4. I'll skip timer, not a fan few tries no puzzle.
5. The drop into final has Easter Hunt a Companion, not a fan.
6. Put Companion down in the middle of laser path. Go near laser field and see the room sphere at. Go there by portal.
7. Ignore it, your aim is High Dive to Mole Pop for Reflective, do so now.
8. Reflective to hit trigger to laser field and stairs.
9. Go piston platform and drop the stacks by portal to you. Reposition piston to sphere room, walk there, position again so you can drop a cube on that button while standing on piston.
10. Figure last step yourself, tl;dr.

I am actually annoyed at the first part, Peraonally I dont like timed things, and the time to hit the button and get the cube out is tight, andthen I tried a different way and it didnt work either.

Thanks for the suggestion @temporarymanwastaken. Now altered.

It could use a way back to the white room from the exit in case the player solved the laser puzzle the wrong way. I'd also suggest making the floor of the exit area black and the farm walls that don't touch the glass white to prevent portal bumping.

Thanks @Alex.y!

nice

Thanks Cpt_Owenbrau!

nice

@aFather: all along the back wall and on the right!

Ok, I tried a few times to find this surface, even standing on the cube at spots with my back to the laser curtain. I have got the jumping/bouncing and shooting in the third room down to an art now eventhough I was cursing it at first, so one last hint please: is the surface on the left or right of the cube/ball dropper on the ledge? I am going to finish this level!

@EnderTheKid OK. There is a surface and yes it is quite difficult to find. The surface is on the upper ledge behind you after you enter this third room. It's easier if you use the companion cube to give you a little extra height...

The part where you have the cube, and there's a laser field? People are saying there's a surface on the section way up above me, but I can't see it :/

@EnderTheKid I know one thing I should have added was auto-save points - apologies for that. Which parts are you having difficulty/dying on?

Bruh. This is so difficult. I kept dying and getting transported to the cery beginning. After about twenty minutes, I gave up. It seems all of the place and confusing.

From my own experiences, the timer is best used as a delay mechanism or to attach them to gel droppers to reduce graphical overhead. Seldom do they make good reflex puzzles. There are only three puzzles that come to mind that I have played where reflexes were tolerable and actually enjoyable, all by Goose (no relation to me):
http://www.steamcommunity.com/sharedfiles/filedetails?id=77625577
http://www.steamcommunity.com/sharedfiles/filedetails?id=78633280
http://www.steamcommunity.com/sharedfiles/filedetails?id=363184749

Thanks for your comments and for playing!
@Julius I never spotted that, thanks. But I don't know how to fix that bug?!

@wgs Thanks for the critique. Maybe an extra 1 or 2 seconds to the fizzler timer may solve the X panel issues. I was just trying to make the time as short as possible. Still trying to perfect the art of chamber making!

It was OK for a test. The x-symboled panel was annoying to get activated and find the portal surface to reach the ball was hard to spot. I thought I was stuck or trapped or skipped a crucial step. Needs refinement.

It's really nice test! But there is a bug when you put the reflector cube on normal cube in the fird room, you can remove this normal cube, and then reflector cube will levitate.

@lfairban I don't want to give too much away, but have a look at the spoiler in my previous post. That should give you a bit of a clue to help you complete the room.

I'm not finding a way out of the room FD is in.

Here's a clue: When you enter that room, look up and behind you - there's a ledge. It's possible to portal to it...

It's a good chamber! I'm not sure if I'm missing a passage here... I'm currently stuck in the room with the laser grid with just a companion cube and I'm unsure what I'm supposed to do here since where I come from is blocked.

Nice!

I thought the cube placement (and being able to "catch up" to the rising platform) was one of the most fun parts of the solution; I wouldn't change it at all!

Thanks dmuk. I always thought the ending was a bit messy ( placing the companion cube to make the platform rise ). Did you have any issues with that? I'll try and improve when I make another chamber.

...but getting from one to the other is less than obvious, but possible. I had the most fun with the last stage, working out the proper sequence and what to leave where. Needless to say, I had a ball! This is a nice chamber to rank; I'd call it an easy-ish medium.