Ah, it's reassuring to see other people getting mad on that triangle. I am very curious to see the solution for that thing in particular, as I found all the other CSS puzzles way easier :)
My personal best (9px left): https://i.imgur.com/A0LIDxT.png
My personal best (9px left): https://i.imgur.com/A0LIDxT.png
I've updated the last puzzle to remove any transforms, so it should be much easier now, and you can move on to the next stage.