At hint to usability: the link in the last line of your description is only text. Make it a HTML link so that the successful player of your game can click on it to get to the decoder. In my case, I had the code but then I copied the link text into my clipboard to use it in a new tab, out of habit, destroying the webcode itself on the process. Stupid, yes. But help your players to avoid such mistakes by making it a real link ;-)
The game itself was oldfashioned... eh, a classic. I haven't been moving by arrow keys instead of WASD in a long time... :-)