This is a fast paced game that any number of people can play. You could even play it as solitaire. If there are more than 10 people it could get a bit crowded. Unlike other games that are this flexible, it is a game of strategy. But you do not have to consider too many distinct factors. Things do have to be worked out in the head, and that is what makes this fun.
The board is a simple 16x16 squares. This is the playground of the 4 robots - each with a different color. These robots, when activated go along a straight line until stopped by other robots or by a wall. The board is surrounded by a wall, the central four squares are walled off as well. Other than that there are small angled walls on two adjacent sides of several squares. In these squares are targets that the robots seek - 4 distinct ones per color, and one universal. Each of these 17 have a matching token.
This is how you play: One person pulls out one of the 17 tokens at random. The appropriate colored robot is supposed to reach the corresponding location on the board by ricocheting off walls and others robots. Each linear move by any robot counts towards the number of moves. This is where the strategy comes in. In your head you figure out the minimum number of moves needed to reach the target. You then announce it. Whoever announces a number, a one-minute countdown starts (hourglass or stopwatch). If someone can better that count within a minute, that is allowed. Otherwise at the end of the minute the move is demonstrated and the token goes to the winner. The robots are left where they were at the end of the first set of moves. Now the next token is drawn and the moves contemplated.
Online versions are available, but these seem buggy. It will be fun to program for the best moves. One can print the board and play with lego pieces as robots - a poor mans way. The original board is of course much better to play with.