Did you guys ever play "impossible mission" on the C64. It was one of those games that was really impossible as far as i was concerned but was simple to learn with simple rules and entertained us kids "foooooreverrrrrrr"
The setup:
A random generation of rooms leading away from 6 or so elevator shafts. To the left or the right
The only way to get to another elevator shaft was to go through a room. With in the rooms there were robots that would either:
a) Just stand there zapping a sertain distance every couple of seconds
b) Move left and right on a level and zap at the ends in bot directions
c) chase you as soon as you were on a level (the robots where much faster than you) and zap you
I can't rember if you had 1 life or 3.
In these rooms you had to collect puzzle pieces behinds objects such as computer terminals, furniture and the alike. Once you had a certain amount of puzzle pieces you could go back the elevator shaft area and then try and figure out some of the puzzle piece. The were superimposed ontop of each other and , you could turn them and mirror them. There were about 4 pieces to each puzzle and about 10 or more to solve (I never got more that 4!)
In the rooms you had little elevator that you could go up and down the levels with the diffrent robots and furniture. Once the platforms where up and you fell down to a lower level, youi could reset the levels by going to a terminal screen and using a 'pass' to reset them, but these where limited. Offcoure if you fell through the bottom level you would die and a lovelly "aaaaargggggggg" would screemed by the C64
You could get more platform elevators reset passes or robot dsiabeling passes by going to a special room where you would listen to 3 notes and you had to repeat it in the same order. Once you got that pass, you got 4 notes, then 5 then 6 then 7 and then damn hard with 8!
Once you had all the puzzles you were to go to a special room and pass a door, where you had one more thing to do, but i never got to that. There were urban legends that some people had but i doubt it
Oh and offcourse there was a 2 hour time limit, just to make it impossible
anyway it was 3 games in one, simple to learn, random generation of where the rooms where, what were in the rooms and where, ie robots and furniture, and then where the puzzles where hidden, were also random. Not all furniture had a puzzle piece. So there could never be a walk through like most games to day, it always evolved into a new puzzle, just as impossibe as the previous.
Ok now i need to take a breath
On a side note, it was amazzing that they could make the C64 talk. After all they only had about 48KB of memory or so (the rest was OS) Which fit the whole game and some speech.
ProfessorPap 
JohnnyEnzyme 
QuirkyCrow
(but the singleplayer game probably wont have much replayability in itself)