Sure! Happy to elaborate.
In the main mode, the game feels well balanced up until the boss. I played twice with different builds (more attack vs more defense) and both times the boss felt like a significant wall compared to everything before it. Didn't feel like strategy mattered much there.
In time-attack, the final section is where it gets rough. The asteroid gauntlet hits really hard, much harder than the enemies themselves. The enemy count is manageable but maybe slightly too many. The asteroids though don't feel fair, the damage they deal is way too punishing compared to the rest of the run.
Hope that helps!