The idea is to build up the solid shape indicated by the views to the left - but only using the number of cubes given. There are 10 problems, called figuur1 to figuur10. Be warned: they are not easy.
This is a Java applet, so if you don't have applets enabled it won't work. In addition to clicking in order to place or delete blocks, you can also drag the puzzle to rotate it around and get a better view. The arrow pointing at the grey grid shows you which direction is the front view.
The scoring system requires a little explanation. A dot will appear next to the name of the puzzle (in the lower-left window) when you've solved or almost solved it. The tricky thing is that the dot will be green if you're almost there, and yellow if you've fully solved it. Those of us here in the USA would tend to assume the opposite, because of our traffic light colors. To be exact, green means "your shape matches the front, side and top views, but doesn't have the desired number of blocks" and yellow means "all views match and you also have the correct number of blocks."
( Possible spoilers.Collapse )