A particular game that offers a nice challenge.
In Mr. Cool, you play as a little Commodore 64 (or at least I think that's what the thing is ). The point of view is from the side, like many C64 games. The field is composed of various little squares, in a pyramid fashion, and you have to activate those squares by jumping on them, in order to advance to the next level. Your C64 can jump down and up, so you can only proceed in zig-zag. To make things difficult, flames come from the sides of the screen, and if they touch you, you are melted (yes, pretty strange). Also, when you get to the higher levels, the squares need more and more hits to be fully actived. The jumping up-and-down is fast enough not to let you get bored with it, but some variety could've been used. This is pretty much the gameplay... but something esle can be said about the difficulty level. The game is not that hard, but the longer you play, the trickier it gets. At some point, it does become frustrating, and you might be tempted to quit the game.
Graphics are to be considered for what they are - 1983 graphics. They aren't even horrible. True, the background is only black, but the flashing of the squares gives for an interesting effect. Compared to other games, it's not so bad.
Sound, actually, is not so great. Other C64 games already had music, while this one is almost completely void of any kind of sound effect, except when you jump on quares, "tic-tic"... but at least it's not irritating.
I cannot really tell how long the game is because I never completed it, but you should know that many C64 games were short, because they were meant to be played again and again. This one is no exception, and although not as addictive as games (Wizard of Wor, for example), it can be a nice way to pass some time... especially if you have the patience required.