The Spectrum version of JSW2 had a very useful cheat from the point of view of a developer, which used the Cartography room, and I duplicated it in the MSX version. I also added a couple of my own, so that I would be able to prove that every room could be navigated, and every object collected, since there was no way that I could actually successfully play the game all the way through.
Unfortunately, access to the cheat involved pressing multiple keys in a way that emulators appear not to support (it may be a limitation in the Windows keyboard).
If you're running using an emulator like blueMSX that contains a debugger, then you can do the following:
Set it running, and before you start a game (that is, while it's playing the Moonlight Sonata), interrupt it with the debugger. Display a hex dump of ADAF. It contains 28, and the next byte contains 51. Change both to zero (you're changing a conditional branch into a pair of NOP instructions).
Now, when you start the game, the cheats are accessed via three function keys.
F1 displays the Cartography Room, but with a flashing cursor which you can move around using the cursor keys to choose the room you want to put Willy into. Press SPACE to go to that room, and then move the cursor around to choose where Willy will appear in the room. Press SPACE again, and the game continues from there.
F2 toggles single step mode. While in single step mode, the game waits for you to press a number key (note, the key pad keys don't work for this), and advances one step for each press. Note that if you want to make Willy move or jump, you have to be pressing the appropriate key WHILE you press the number key.
F3 toggles infinite lives mode. While in this mode, Willy's count of remaining lives doesn't decrease.
