it is rather unusual isn't it... it's something I just stubled upon one day when fiddling around... I used to have it tiled on my windows desktop but it started playing with my head so I removed it...
If you flip each character (either x or y) depending on which quater of the overall tile you're working on, you can inverse the bulging effect... and... if you're really clever you can merge the two, and then tile it so you have a screen that pushes in and out... but really it's not...
@PK: I've often thought about practicle applications of it... I can only assume in demo - or some freaky alice in wonderland type level background... ?!