An implementation of the 2048 game for the Apple //
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apple2048.xcodeproj
apple2048
README.md
apple2048.png

README.md

Apple2048

This is an implementation of the game "2048" for the Apple // series. It requires an enhanced Apple //e, Apple //c or Apple //gs. The binary is a ProDOS system file.

Instructions about how to play are displayed on launch. You can bring up the instructions at any time by pressing the 'h' key.

Apple2048 Screenshot

Download a disk image

Implementation Notes:

The game logic is in game.c and I believe it reproduces the basic behaviours of existing 2048 implementations. The code for animating tiles is mostly still written in C in anim.c and is messy. There are lots of opportunities to improve performance in animations.

The way animations work is:

  • Text page one is copied to text page two.
  • Text page two is displayed.
  • The next frame is prepared on text page one.
  • Text page one is displayed
  • Repeat all of the above for the next frame.

The copying of page one to page two is implemented in assembly. There is a problem with using text page two. The Apple //GS has a "bug" where shadowing of text page two from bank $00 to bank $E0 is not implemented. This lead to the creation of the "Alternate Display Mode" CDA which did this shadowing in software at a performance cost. Because I am using page two, early versions required "Alternate Display Mode" to be on.

But, I worked around this in software. At startup, the code detects if it is running on a GS. If so, it choses to use a different implementation of the assembly routine to copy from page one to page two. This implementation switches to native 16-bit mode and does a copy from $000400 (text page one) to $E00800 (text page two) right into the $E0 bank. This avoids the need for shadowing $00 to $E0 and it now works as expected on a GS even with "Alternate Display Mode" off.

Possible Improvements:

  • Make the animation code not suck so much.
  • Optimize the tile drawing code
  • Wait for the VBL interval before switching text pages to avoid any tearing.