Save the Ninja Clan

Video Guide

Text Guide

As you enter level 19, proceed through the level as normal. Once you get past the swinging sawblade and enter the area with the horizontally moving springboards with saws, jump across as normal, but as you jump off the second spring, jump towards the left and you'll land on a ledge with a flashing wall, jump in the wall and run to the left, the dev/creator will comment on it, and you'll be transitioned to another area, run to the right till you hit a wall, run back to the left and keep running (and jumping! [Not required]) till you freeze and the game fades out to a green text screen of the game resetting, and then to a multicolored screen, where it "freezes". It will take you back to the main menu, hit continue, and the achievement will pop.