slowmo bullet hell is now my favorite genre of games.
i'd have harvested for so much longer time, i'd say the intervals between events can be twice as long.
movements are great, the balancing of movement upgrades is very satisfying. but when still moving backwards (after letting go of the key) left and right should still be inversed.
for basic gamification reasons there should be more health (and also more damage). instead of starting with 3, start with 30, one hit deals 10 dmg.