Your game is an interesting take on space invaders so had to try it out and your game is pretty fun so somebody had to make a video of it eventually we just happen to be the first ones.
Having 60 levels is good to have enough content for the player but it needed a break to save progress or something big like a boss to fight to feel more like your accomplishing something per stage. A level select could let players choose where to continue from if they want to just finish the game or get a better score by starting from the beginning. It allows for more freedom than saving from one specific spot.
Yeah we had a lot of fun with it just fatigue did set in after a while mostly to not knowing how long we had left.