The current rules (for the level leaderboard) say "Waves mode, use the speedrun option. Timer goes off ingame timer." Waves mode no longer exists, and neither does the speedrun option, which means there is no in-game timer to go off of anymore.

I'll be submitting a run for World 4 in Campaign mode, with time based on the video (where the starting condition is when you gain control in the first level, and the ending condition is when the boss shatters, exactly as in the old speedrun option). I recommend the rules get updated accordingly.

Is it better to put all current runs into a Legacy category? Because the game has changed quite a lot since the version you are referring to, including rearranging all the levels.

Here are the changes that I think are necessary.

1. Rules should be as follows: (X corresponds the world number) 'Complete all levels in World X. Timing starts when you press the start button, and ends when the boss shatters. Skipping and returning to the menu is not allowed.'

2. All current IR speedruns should be put into a Legacy 'category group'. 10 new categories should be added, which corresponds to each world. (that is from World 1 to 10)

3. Full Game Run should be changed to Any% with the rules as follows. 'Complete all worlds in the Campaign mode. Timing starts when you press the start button of the first level of World 1, and ends when the boss of World 10 shatters. Returning to the menu is not allowed. You may only skip one level per world. You may not skip boss levels.'

I believe that Flat Heroes is an insanely fun game to speedrun, so I believe these new rules can help people better time speedruns of this game.