Great game, great series, but can't find any way to play part 4. It seems like it was on Armor Games, but isn't accessible anymore due to Flash being shut down. I went to their own website, but can't find the game on there. There are ways to buy/download the whole series for PS4, Switch, etc., but the only way to get it on PC seems to be buying the whole series on Steam or similar sites. I understand that they have to make money somehow, but putting the final part of a free series behind a paywall is pretty disappointing. I assume that wasn't their intention from the start (since it seemed to be on Armor Games), but that seems to be how it turned out. I wish they would post it on Newgrounds or make it easily accessible on their site.
Regardless, chapters 1-3 were great and still worth playing, even if I can't finish the series.