The artwork is looks clean and is easy to parse. I like how you spawn an asteroid on top of the dinosaur so the player really does have to keep moving. it's interesting trying to move out into open spaces to maximise your chance of always having somewhere to run to. I haven't been able to make it to the full 60 seconds yet!
Not sure if you intended for the dinosaur to walk upside down as an aesthetic decision, but just in case it helps there is an example here for how to flip your sprite: https://easel.games/docs/examples/flipping - in either case very cool that you took the time to learn Easel for this!