add 'cornering' keyboard mode

[filbo]

Hi, this is beautiful work!

There is one significant difference in play from the Apple ][ version I played way back in college...

On the version I was used to, holding down two direction keys at once would follow corners. Suppose you're on the bottom and a ladder is to your left. If you hold down left+up keys, you will move left until it becomes possible to move up (i.e. you reach the ladder); then you'll automatically 'corner' and go up.

I'm sure there are all sorts of strange logics to figure out for this, e.g. if you're on a flat surface up in the air, going right, and to your right is a rope, does right+down keep going right or does it drop as soon as you start swinging along the rope?

Anyway, this greatly enhances play for me, so I'd like to see it as a 3rd control mode. (Not sure if it should be a 3rd one, or a 2nd toggle -- I'm not sure what it would mean, how it would play, to have 'keep going' + 'cornering' at the same time. It's a very long time since I played a lot with this mode. I think it may have been like:

• hit right (and release): you move right until you hit something else
• hold down right, start also holding up, hold both: it corners
• hold down right, start also holding up, release right: you will stop moving unless 'up' is currently a possible movement
• I don't think it was possible to 'hit and release' two keys at once, i.e. to leave yourself in a persistent 'cornering' mode without actually continually holding down both keys

https://archive.org/details/lode_runner_the_legend_returns_windows_3.1 displays some version of this behavior (poorly implemented, it seems to forget you're holding down one key or the other after a couple of cornerings).

https://archive.org/details/arcade_ldrun seems to fully implement it (and its answer is 'drop off a rope if you're cornering down'...)

https://archive.org/details/Lode_Runner_1983_Broderbund_US also fully implements it, and seems very smooth and nice -- except I can't find the 'dig' buttons anywhere! (Also, peculiarly, Ctrl+K seems to mean 'joystick' while Ctrl+J means 'keyboard', an odd inversion!)

...

Well, in fact, I was not able to find an archived version which behaves quite like I describe. The Apple II versions work like your Apple version -- hit a key, keep going that way until you hit something else (don't have to hold the key down). The others behave like I describe, except you must hold down the key(s); there is no tap-and-keep-moving behavior. Yet, I think the combination would be best. Tap one key, move that way until you hit something else. Hold two at once, and you 'corner'. With a key to stop moving (space by default), and also if you tap an unusable direction (e.g. 'up' while you're on flat ground), you stop.

The emulator versions with cornering are more pleasant to operate than yours; but yours is entirely better in every other dimension.