From a programmer's point of view, how can a snakes and dots game consume much more resources than many other more advanced games?
All the calculations are done by the CPU, whereas other computation-intensive games tend to make use of the GPU. You can observe this by looking at your CPU monitor/task manager, and your graphics driver configuration interface (if you have a fancy card).
When I load the slither game my GPU temp doesn't increase at all, whereas the CPU temp climbs steadily, and the game immediately swallows half of my cores. CPU use further increases in "busy" periods when there are many other players interacting in a small area.