Nope, didn't enjoy this. A shame because it seems lovingly crafted. But it's the gameplay that really detracts from the experience.
For starters, it is a flappy bird with gravity switch gates. Nothing that new there. To be fair its' presentation is well polished, with a lovely minimalist feel. The music is OK for the first few plays - but like all things, grows annoying on the umpteenth play. Mute button needed.
You don't score when passing through gravity switch gates. Seems unfair, since these gates force you to the edge of the playfield, making the next gate (which you can't see yet) potentially much harder to pass through. Maybe +1 for gravity switch gates and +2 for normal gates.
Didn't find the controls responsive enough (there is only one control!!) Sometimes when I press space it doesn't respond (especially near the top of the screen - if I press space near the top of screen, typically I lose control for a few milliseconds (and plunge to my doom)).
Game is too fast to really enjoy - this is kind of linked to the next issue.
Because the "jump" is a prefixed height that is easily larger than the gap in most gates, then if you don't have the correct position before reaching a gate and have to execute a jump mid-gate (as you are passing through the gap) you usually hit the top part of the gate. Combined with the fact that you only see the next gate as you are busy passing through the current gate, this makes the game EXTREMELY UNFORGIVING: you die a lot simply because you don't have the time to get your flappy-square into the correct position BEFORE the next gate to execute a jump that will make it though... To fix this you need to widen most of the gates and increase the forward view to at least 1.5 gates (i.e. as you ready your jump for the current gate, you can see the next one and plan what you need to do). Currently it's just as easy to aim for the +10 gaps (since these too require perfect positioning beforehand - but are far more rewarding).
Quite often I would die having "collided" with something. BUT since you freeze the position of everything before the screen fades out, I can see that my square has NOT come into contact with anything yet. Annoying since quite a few times I'd die while passing a leading or trailing corner... but I haven't collided with it yet, and I have no reason to think that I would have... (yes, sometimes I have to admit I would have collided with the corner - but it is those times where I'm sure I would have made it that is annoying). I guess you need to tighten the hitboxes??
No, I did not experience any lag.