A little conversion for the new year -- a port of the 2600 game Raiders of the Lost Ark to the 8-bit. It's not one of the most graphically intense games, but it's one of my favorites as I always thought of it as a more advanced Adventure. It requires 48K of memory, but should run on an 800.
Most of what is in the 2600 manual applies, except the B&W switch... which didn't work even on the 2600. Press Start to restart the game. The original game had a clunky two joystick setup where player 1 controlled the inventory and player 2 controlled Indy. This works in the conversion, except reversed so that joystick 1 controls Indy. Two other control schemes are now supported. The keyboard can be used to control the inventory, by ,[ and .] to move the cursor and space to drop items. You can also connect a Genesis 3-button gamepad and hold down the C button to control the inventory, with B being the regular action button. The gamepad must be connected when pressing the action button to start the game from the Well of Souls for the game to recognize it.
- The original cartridge is an 8K banked cartridge. It about doubled during conversion because I expanded a lot of playfield data; it could probably be crunched down a lot since the playfield data is very sparse. The original code/data is all relocated down, but there are still some places in code where the high address byte for data is hardcoded.
- Raiders doesn't use replication, but it uses HMOVE a lot, and worse, has no less than four different display kernels which use a 'display list' to drive both player 0 and several different hardware registers. I basically had to totally rewrite three of them. One annoying GTIA issue I ran into: can't detect collisions between missiles. Bad if you're emulating the ball with a missile and then find a M1-BL collision check in the code.
- I spent more time verifying the graphics this time against the original game in Stella and it should largely match the 2600 version pixel for pixel. This was needed because the map room actually became unplayable if the VDELAY settings on the sprites weren't just right. Notable deviations: the left basket in the marketplace is a scanline off because of a timing issue in the display kernel and the lower temple entrances aren't squared off when the doors drop; those were too much of a pain and too minor to bother fixing.
- The sound driver in the game is primitive, but the way it does sound effects is amusing -- it writes the same value for frequency and distortion.
- No PAL speed compensation this time -- Raiders relies a lot on playfield collisions and some of the position checks and level boundaries would probably break if Indy could move faster than one pixel per frame, so just running the vertical blank processing 6/5ths faster won't work. Color compensation is also difficult because colors are embedded in the display lists.
- All secrets and most bugs should be replicated, including the Yar and the signature. A couple of bugs didn't carry over because they are caused by wigging out the TIA sprite placement (walking off the right side).