I've done some testing of the differences between the two difficulties (first option in the options menu, defaults to Normal, can be flipped to Easy).
Here's what's different on Normal that's notable to a speedrun:
- Most normal enemies have more HP. The generic trash still dies to 1 rocket or rider kick, but other things may need 2 hits; things that needed 2 now need 3.
The last two points are the most important. While most of my mech fight strategies will still work, you'd have to spend time defending to recharge between offensive flurries; a LONG time recharging on the final fight. I wouldn't be surprised if this adds 3 minutes to the run on its own.
Of secondary importance are the other two points. More enemy HP means more backboosts while trying to rider kick through enemies, that's about all. More boss HP makes bosses take longer because at no time are you in danger during boss fights; it's just more time for no difficulty or style gain.
In general, Normal difficulty is "the same but takes longer". I personally feel Easy makes a cooler looking run even if you execute optimally in both difficulties. However, these differences make comparing runs between difficulties unfair.
For now I've added a difficulty field to the leaderboard so it's clearer. If someone besides me takes up running the game I'm more than willing to split the board into two categories.
Just noting this all for the record if anyone gets curious.