iiinova — where your digital self keeps evolving

Retro Game Mechanics Explained

@rgmechex.com

A YouTube channel about video games & programming. Channel: youtube.rgmechex.com Discord: discord.rgmechex.com Inquiries: inquiries.rgmechex.com

Posts Replies Media

Retro Game Mechanics Explained @rgmechex.com · 25/01/2026

Next video coming soon, and now available for early access for supporters! Going to go a bit in depth about why some arcade games start up with a random mish-mash of tiles... patreon.rgmechex.com

An assortment of 8-bit graphics tiles in a glitchy, but ordered diagonal pattern; "Early access on Patreon & YouTube Membership"

26411

Retro Game Mechanics Explained @rgmechex.com · 07/05/2025

Watch out, in the dark you might find a bug! Subspace and the entirety of the Super Mario Bros. 2 level format explained in an upcoming video, available now for Patreon supporters and YouTube channel members! patreon.rgmechex.com

3697

Retro Game Mechanics Explained @rgmechex.com · 15/01/2025

You can make it through all of world 1 of Super Mario Bros. 2 without beating a single boss, but you need some clever tricks to make it happen. New video soon, and available now for channel members and patrons! patreon.rgmechex.com

05110

Retro Game Mechanics Explained @rgmechex.com · 05/11/2024

GCC Developer Steve Golson left a few comments on the recent video! He actually looked into an older version of the source code to see what exactly happened, and it looks like the code worked as intended at first, but was modified and broke during later development!

@13:46 Yes, it was just an error!

I disassembled the earliest version of code I have (this is actually Crazy Otto). It shows the correct patch for all four monsters:

2745: 2A 0A 4D ld hl,($4D0A)
2748: 3A 2C 4D ld a,($4D2C)
274B: CD 2F 3F call $3F2F
274E: CD 66 29 call $2966

277B: 2A 0C 4D ld hl,($4D0C)
277E: 3A 2D 4D ld a,($4D2D)
2781: CD 2F 3F call $3F2F
2784: CD 66 29 call $2966

27B8: 2A 0E 4D ld hl,($4D0E)
27BB: 3A 2E 4D ld a,($4D2E)
27BE: CD 2F 3F call $3F2F
27C1: CD 66 29 call $2966

2800: 2A 10 4D ld hl,($4D10)
2803: 3A 2F 4D ld a,($4D2F)
2806: CD 2F 3F call $3F2F
2809: CD 66 29 call $2966

Note they all have the same CALL $3F2F. So originally we had it working, all four monsters random, and then we screwed up INKY and SUE when we adjusted the patch code to align with 8-byte boundaries.

Ok that is seriously depressing. A bug report for work we did in November 1981, 43 years ago.

518133

Retro Game Mechanics Explained @rgmechex.com · 03/11/2024

I did end up making that followup video about Ms. Pac-Man and why I think Inky and Sue were not made to move randomly at the start of each level. There's a bunch of stuff to learn and explain about arcade hardware! Available to watch now on Patreon! patreon.rgmechex.com #rgme #pacman #mspacman

A diagram of a circuit board with a few of the integrated circuit chips highlighted in red. "Early access on Patreon!"

0262