Sunday, 29 December 2013

There was movement at the... errr... building site

In a nutshell, Mario runs left and right now.

The areas in the other listings that tend to be completely devoid of any analysis are the 'mechanics' of game-play, such as animations - and the animation of Mario himself is certainly no exception. Tonight I managed to decode the basic left-right animation logic and now Mario can run back-and-forth along the bottom girder, and even changes height correctly.

The sprite animation logic is - interesting - to put it mildly. For some inexplicable reason, rather than a simple look-up table, animation sequences are represented by bit pairs packed into hard-coded bytes strewn amongst the code and look-up requires loops of rotations, masks, compares and register copies. The same routine also (reportedly) handles barrel sprite animation (that have their own animation cell sequences) just to further complicate matters. Hmm...

Also, it's not noticeable during game-play but Mario actually 'slides' for 2 frames between sprite changes when moving left/right.

I also tried to fix the 'slow' speed, without luck, so everything is running about 50% atm. Once I find the reason and a fix for it, I'll upload a short video of Mario running across the screen.

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