I know there was definitely more to do but first time through, I enjoyed the concept as well as the variety of mobs, the mixing of mob types, and their different bullet patterns. As someone who usually doesn't play too many games, at first, I had some difficulty understanding the forward and backwards arrow mechanic as well but I think once I got the hang of it, one if the great things about it is that it basically trains your from there to get use to it, like the type of muscle memory that games make you build in order to use them with quicker reaction times. I don't know the max score but one of the things I found was that I wasn't really incentivized to explore more. Sometimes I would see gems and such that I could get with more bombs but I was most driven to beat the game and if I thought my score was high enough to move on to the next stage without too much score casualty, I did. But again, take that with a grain of salt because I'm not the completionist-type.