Hi, thanks for taking the time to play it and also to comment.
Totally agree with you about level design. I had a concept of dropping a box out a chute if one got destroyed, but time got the better of me, and in the end the levels are so short all it broke was the story aspect really. Definitely can be improved on though, as well as adding more uses for the portals. Maybe for a future project.
As for the lag, I've never heard of Gamemaker specific Windows 10 lag, and never experienced it, and I've been using GMS for ages. It only runs at 30fps, and just did a frame test, and it's over 1000fps. The code is pretty simple. If you're getting it on other projects might be something on your rig.
Thanks again for the comments.