I briefly considered doing something like this myself, there are some interesting ways to monetize this if you manage to become the web circuit designer/simulator.
Some things you might want to consider:
* be more Mac friendly -- backspace instead of delete, Cmd instead of Ctrl on Macs
* It feels unnatural that I have to press a button on the menu to enter a placement mode. Something like drag and drop might be more natural.
* There's no obvious way to delete stuff with the mouse