A 'Software Toy' by Maxis, where the player builds a skyscraper floor by floor. Created by Yoot Saito, SimTower has the same goals as its brethren Sim* games: Nothing. The only thing to worry about is having enough money to continue building.
Income is gained with offices, condos, hotel rooms, and shops, while money is spent on new building and maintenance. At certain points, if the tower has enough population, and prerequisite rooms, the tower will increase its rating, which starts at 1 star. Each additional star will give the player access to new room types.
This is an old game, and as such, there are some design limitations. Don't even try to make a stairwell to the top; the game won't let you use that many. Elevators are also under a limit, which always causes problems.
There is an unofficial sequel, Yoot Tower, though there are few major improvments.
If you think this writeup is similar to Yoot Tower's, it's because these two games are virtually identical. (Noder's Opinion)