I like the idea of collectables.
You tend to see them a lot in those endless-runner style games, which yours is a flavour of also. You could opt for simple, all the same collectables, like coins (although something which “fits” with your game theme would be better), or have a variety of them that do different things. Some could be power-ups/down (increased speed / slow motion / jump ability and so on).
The tutorial I used was from Brackeys
Thanks for the clarification and the URL, it was merely coincidence that you posted your game not that long after I’d seen another so similar, most likely they had been following the same tutorial. You can create a really challenging and fun game from this, often the simplistic nature of it, cubes / spheres / limited colours etc can really add to the overall feel.
also I have no experience reading debug screens
Debugging WebGL is a little less straight forward than locally via Unity, it can be done, to a degree, but its best to thoroughly playtest and check locally where you can catch the errors.
I cobbled something together ages ago for people who ran into issues after publishing a WebGL build, it may be useful, here’s the link just in case;
I look forward to seeing any further update you make to this game, especially if you add some collectables!