there is a lot wrong with the skill tree. energy rocks shouldn't be before getting something to use energy on, it's an active downgrade. spawn rate should before quantity up as you hit the roadblock of not enough rocks spawning before energy or health become a problem. crush damage is worthless past level 1 because the spawn rate and crush/sec is so much better. getting blue rocks to spawn shouldn't be so far off since you run into 5 things that use it before you can even think about getting it so by the time you can buy it you're not making a choice since all relevant upgrades have already been obtained. overall progression is just way too slow, after maxing out crush/sec and blow strength my profits flat-lined and no upgrades really helped improve things