Spindizzy is a game that I played when I was in high school back in the 1980s for hours and hours on end. It is a simple game on the surface - navigate a maze-like environment and collect gems. There are several elements that make it more challenging than it at first appears. First is momentum. Your "character" is a spinning top (pressing "i" will change it into a ball or a different top, but I find the default is the easiest to use) and the longer you move in one direction, the more speed you pick up.
The only good way to stop is to move your controller (keypad or joystick) in the opposite direction. The spacebar works as a brake, but it also depletes your time very quickly whenever you use it, and so it's only useful in rare emergencies.
Another element that makes it tricky is that the board is set at a diagonal. The "up" movement on the controller moves you in a diagonal up/right motion, for example.
Each board (and you can see a full map by pressing "m", but it only shows you where you've been and where you haven't, it doesn't give details) has its own challenges. Some, especially near the beginning, are very simple: a flat room with a nice walled
edge around it to keep you from flying off over the edge and falling to your death. Others have ramps (which you need to build up speed to climb up) and some have no safety wall. Some are narrow paths that you have to carefully pick your way along without falling off the edges. Some have gems you can't reach until you've gone to another room and re-entered from another place (for example, something too high to reach, but another board has a way to get up higher, and an entrance back at that higher level). The further you get in the game the more difficult it becomes, and the more fun.
It starts out seeming like it will be a breeze, but you quickly become addicted because you feel that it looks easy, and if you just try once more you'll get it, but instead it is deceptively hard and your "once more" will turn into hours of play. I recently put this game on my son's computer, and even though he has grown up with games like Halo 3 and World of Warcraft, he finds this game fun and engaging.
The graphics are simple, but the nature of the game doesn't require anything more complicated. Give it a try - see if you don't get hooked!