This topic has come up before: Demos /w "Extra Stuff"
The demo of I Have No Mouth, and I Must Scream also includes unique content not present in the full game - a non-interactive trailer explaining the background, and providing gameplay instructions. The music is also a bit different.
It offers one scenario to play, which was also used in the full game, but in the demo you get to play only part of it and, IIRC, it finishes with an unavoidable bad ending.
https://www.youtube.com/watch?v=9asmJzgVdDw
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Urban Assault's demo has a version of Hyde Park that is noticeably larger, and way more dangerous to play. (Already has Ghargoil II, Tekh-Trak and Speedy to contend with, also a full power Turantal I) and the two missions after that are nowhere to be found in the retail game.
The demo overall is just brutal in terms of difficulty that it feels strange playing it then going into the retail game thinking it would also be brutally hard, but it's not.
“I am the dragon without a name…”
― Κυνικός Δράκων
