I haven't enjoyed a game like this in a long time. It can be found
here.
It is possible to speedrun the whole game in a predicted hour and a half. But the main purpose of this topic is speedrunning the sacred grounds (a secret level after you defeat the four 'final' bosses) which comes included with an in-game timer. It is one of the most difficult levels I've experienced in my whole career of gaming, but the ending is rewarding. I can finish the sacred grounds in about 8-9 minutes, but there was a video of someone which I cannot find now doing it in under 6 minutes.
Besides speedrunning, this is a great game overall. You may be turned away by the graphics at first, but I recommend giving the game a chance before judging it. It really is fun. Incase you get stuck or want to find out how to access the secret level and the other secrets included in the game, just refer
here. To get maximum enjoyment out of the game, you should go through the game once without checking the guide first :]