Been playing with Scratch today, managed to make a pong game after about 2 hours, still needs to tweaks.
Not quite an alterative to 2diy, since it is complex, not suitable for KS1.
Something to use alongside 2diy. It teaches the ideas if flow diagrams and cause and effect, since to can adjust programmes on the fly with instant results.
This will be shown in a subject leaders session soon.
Click the image to play
Check it out - http://scratch.mit.edu/