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Game: World of Goo
Awesome game. High replay value. You don't need a fancy graphics card... :)
I see here that recent version is '0.6.2' but I have played 0.5-1 in my 'xubuntu8.04' repositories, so I played that.
I played what I could. I went through around 7 levels of freedoom. First few of them were nice, even little innovative. But then I stumbled on 3 levels that were just an empty room. Then another one which seemed like just a work in progress. Strange doors, then some storage room which was hell-hard to beat on 4th skill level. I haven't played further as it seems unfinished.
Wall textures look nice. But you can't say that on creature sprites because they look unnatural. Each of them has different style of looks. Some of them are not finished (they are gray with text 'not finished').