Ask HN: Can I create an online verson of a trademarked card game? (UNO)

I've created a few javascript card games [1] over the last few months. For my next project I'd like to create the game UNO. Mattel apparently owns the trademark and copyright for UNO, but I'm not exactly sure what that means. If I create an UNO game can they sue me, or send me a cease-and-desist, or something like that? I'm outside the US if that makes any difference.

I also know that there are dozens of UNO games out there already, I have a hard time believing that all of them cleared it with Mattel first. Are they just hoping that Mattel doesn't notice? Or is it enough to have a disclaimer saying something about "UNO is a registered trademark of Mattel, no affiliation etc."?

I have actually sent an email to Mattel, they have a special email address where people can request permission, but they say it might take 4-8 weeks for an answer, so I thought I'd ask here first :)

EDIT: UNO is played with a special deck of cards, just to be clear, so there is something there more than just the gameplay.

[1] http://www.spades-cardgame.com , there are links on there to all the others.