Magnetic Blocks

The red and blue magnets have opposite poles, the iron magnets are attracted to everything and the wooden blocks have no magnetic force.
Another thing you can do is rotate the camera around to place blocks anywhere you want. Try turning off gravity and seeing how blocks interact. Also try turning off all the magnets, placing the blocks, then turning all the magnets back on and watch them fly together.
If you really want to get technical, toggle edit mode and tap on a block to change its mass, magnetic force and magnetic pull radius.

Have fun!