you could give Construct 3 a go. It's mobile and works in the browser, supposedly they added mobile editing. I own a super narrow android phone so it was unusable to me, but on a pad it should be fine.
Another browser based engine is playcanvas. That one is more a 3d unity like environment, you'll need to code, and will need a source of 3d models, but it's pretty slick how far you can get in the browser.
Good luck!