As Steam Summer Sale kicked off, an important update to Pure Logic was released.
The undo function is now unlimited, instead of the last-step-only undo that has been available so far. In addition, any set signal can be changed directly to the other colour/state, or reset back to the original unset state.
Judging by feedback in reviews and the discussion forums, I think these changes will be appreciated by quite a few. And hopefully it opens up for a wider range of solving strategies.
Enjoy the update, and enjoy the Steam Summer Sale! :)