Using this virtual manipulative you may:
Add blocks to the workspace by clicking and dragging them from the bin in the upper-right corner.
Rotate blocks by clicking and dragging anywhere in a blank area of the workspace.
Connect a yellow block to a blue block by dragging it near a blue block until you see one of the sides of the blue block turn red. Then let go of the yellow block and it will be glued to the red side of the blue block. To unglue a block, click and drag it away.
Sometimes it may be hard to see where you are putting a block because it gets in the way. Hold thekey down while dragging a block to make it so you can see through it and better see where you are placing it.