To activate the built-in cheat:
    1. go to the Credits screen
    2. click on these names, in sequence:
            Dave Strock
            Roy Sawyers
            Peace

The cheat allows you to:


    ==== level selection screen ====

        - choose levels that aren't yet unlocked   (though you can already do this normally with the "load level" command

    ==== edit screen ====

        - go over-budget

        - use all materials, even if the particular level would normally prevent you from using them


    ==== simulation screen ====

        - start an earthquake

        - God Mode:  drag and throw trains, cars, and segments of the bridge

        - manual phase:  control the lowering/raising of drawbridges manually, etc