and you should not buy it because it won't run on your computer
I'm running windows vista, attached is the error message I get.
there is no solution.
At least, not if you're not willing to edit the registry - which the instructions provided by Valve staff could be completely wrong, because they are for windows XP and not vista.
http://forums.steampowered.com/forums/showthread.php?t=984011

I'm not having a problem on W7, but yeah, it's not all that. I do like how it looks sometimes.
EDIT: It reminds me of the show "Little Bear." At least, I think that's what it was called.

On the plus side, it was only $2.50 for while.

Thats why I bought it. Of course it won't run on my PC at the moment but then neither will windows so I'm not too worried about it yet

Honestly, it isn't worth the $2.50 I paid for it.
It is horrendously bad.

Lucidity runs fine for me on Win XP Pro, but I still wouldn't recommended it to anyone. It's lacklustre at best.

Apparently someone forgot to pay a QA team. Oops.
A similar problem occurred with Stormrise on Windows 7, but that at least was understandable because at the time Windows 7 had not been released yet.
Also I love how Valve details registry tweaks to get around problems caused by Steam rather than, oh, I don't know... releasing a client update? Nah, that's just crazy talk. Since the problem seems to stem from Steam itself I bet you the pirates can run this just fine on any OS of their choice.

Is there an XBLA version? I'll just get that.

Yeah its on the XBLA and the demo ran perfectly well.

Good to know, I'm currently on VIsta (SP1) too after my previous computer's unexpected and painful death.
Furthermore I've got Braid to enjoy so I really don't feel the need of trying a new 2D game at this time... Oh, and btw if the steam-powered crap does not work you could try the cracked, p2p-powered one. They usually remove the steam-crap and let you play the game by itself :-P

This is why you fail.

I have WinXP SP3, and while I do not get this error message, the game crashes after I select the language.
I have to set my windows regional and language settings to english instead of czech, then the game works.I wonder who can be idiot enough to program such a mess of a game.

Don't see why, it was flawless for me, shat all over XP even with it being a bit slower at times and having a few niggly bits

Works fine on 7.