WIP: Reversi

[MADrigal]

No news on the Reversi development side?

[carlsson]

I've been too busy with other matters to think about Creativision programming/debugging. With a bit of luck, I might investigate this sometime in the summer, but I'd rather start with a smaller project from scratch to figure out the way to do VDP updates before implementing into the full game.

[Mobsie]

thank you for the update. We all love your game.

[carlsson]

Small update in that I believe I may have solved my VDP issues. Now to improve some algorithms so the graphics run smoothly and some other twiddling, and soon this one might be finished.

[MADrigal]

Woho, that's great news, Anders! I cant wait to play the final version. I'm available for a last-minute beta-test if you need any.

[carlsson]

This is the latest version.

reversi-aug3.jpg

Some of the changes since last year:

• VDP code rewritten so the main program while interrupts are enabled writes to a "command list" executed inside the interrupt handler, should hopefully never cause glitches.
• Smart rewrites of the game board, only positions that have changed will be plotted. This speeds up the flipping quite a bit, now when we have to wait for VBL every now and then.
• New controller: press fire thrice within your move to skip it, in case you have no legal move.
• A number of temp variables moved to zeropage, to fit the game within 4K - currently 19 bytes to spare!

Known bugs:

• Sometimes the sound effects (!) lock up. I shortened the error beep to reduce this bug, but also the start of game sound sometimes locks up. I need to investigate why this happens.
• In two player mode, if either player presses fire thrice, the game ends instead of switching to the other player. This is a pure overlooking by me and hopefully easy to fix, as it works OK vs the CPU.
• On startup, the board is plotted square by square instead of everything at once. I could probably solve this by putting more VDP calls to the list before it is executed at each vertical blank, but I didn't get the results I wanted so I think I'll leave it as it is and call it a feature.
• The boot message says Creativision 1981. I might add code for a custom message, but it'd surely bring it beyond 4K for no real gain.

reversi.zip

Edit: Found another, more serious bug: When grabbing 7 squares in a row, only the last 6 will be flipped, i.e. the one furthest away from your new marker will remain unflipped. I'm not sure if this is a new bug that I've introduced, but it needs to be solved...

[MADrigal]

hi man, i have got your game and will gladly test it!
what surprises me is the "introduction of new bugs" in the game engine, which worked very very well until this revision.
i originally thought that you were having problems with the vdp/interrupts issues, and that was not connected with the game engine.
anyway i'm here to help if you need

[carlsson]

Yes, the latest bug seems to be due to partial redesign of the logic display function, what I dubbed "smart rewrites". I think I have reused some bits for two different purposes, which means that the 6 frame animation of flipping pieces will be mismatched to the distance between markers, up to 7 squares. Before I went to sleep last night, I already came up with an idea how to try to fix it, so given that I have the time, it might be fixed already tonight.

[MADrigal]

Bug found: in 2-players mode, I have pressed the PLAYER1-FIRE button three times and the game ended. I mean: I did not press the 1P and 2P three times each... just the P1.

About the fire buttons: I am experiencing the same problem I had with the very first games coded by Mobsie (he then solved the problem - maybe he could give you a hint?).

That is: when I keep P1 FIRE button pressed, that is in "SELECT GAME" mode, the selected game mode keeps on rolling. Wouldn't it be better to just change the game mode 1 time only, even if I keep the button pressed?
I am familiar with this problem with my Game & Watch simulators. I use an additional variable for that, and the routine looks like this:

Code: Select all

ON KEYPRESS
if buttonpressed = false then
  begin
    buttonpressed := true;
    (do what you have to do)
  end

ON KEYRELEASE
buttonpressed := false;

Hope this brings you an idea how to "fix" that issue. I would consider that a "bug" because that gives an undesired choice to the player who is selecting the game mode. In fact in the end he selects a different game because the button-press routine acts too fastly.

Obviously I am testing the game on emulator only, maybe the "bug" doesn't occur on the actual machine.

[carlsson]

Yes, the skip a move in 2 player mode was already mentioned above so it is on my TODO list. The other about game selection is worth looking into, thanks.