Well, that was fast. I just uploaded the Boss Rush video a few hours ago!
Arcade Mode makes you play the entire game in one sitting, with limited lives. Your score and health do not reset between levels. On one hand, staying alive becomes harder, but on the other, you'll get an extra life after 100 points and then every 200 points after that. Play well and try to rack up combos and you'll never have to fear a game over.
...I still have to fix some bugs though. I have no idea why your health straight up drains to zero at the end of Fire Fortress.
At this time, SuperFreaksDev has 2,285 views for I Wanna Be the Guy spread across 30 videos. The game makes up 4 hours of published video on his channel, roughly 6.85% of I Wanna Be the Guy content that SuperFreaksDev has uploaded to YouTube.