17 May 2017

Sega Mark III - Paddle Control games hack

Few Sega Mark III games were made to be used with a "Paddle Control" in a similar way as Arkanoid or Pong.
It's impossible to play them with a standard pad.
So far I've made a hack for these games to be able to use a standard pad:
- Alex Kidd BMX Trial
- Woody Pop

Alex Kidd BMX Trial:


Cheksum has been fixed so the game runs fine on a US/EUR console (if someone ever wants to make a cartmod).

Technical part:
Angle is strored in RAM at address $C022.
$00 corresponds to the most left direction.
$80 corresponds to straight.
$FF corresponds to the most right direction.
So:
- if no direction is depressed I write $80 at $C022
- if left direction is depressed I write $00 at $C022
- if right direction is depressed I write $FF at $C022

Woody Pop:


Again cheksum has been fixed.

Technical part:
Bar position in stored at address $C012.
$00 corresponds to the most left position.
$FF corresponds to the most right position.
So:
- if no direction is depressed I don't change the value at $C012
- if left direction is depressed I decrement the value at $C012 by 2
- if right direction is depressed I increment the value at $C012 by 2
This way the game is playable with a reasonable bar speed.




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