C64 Games memories - Skool Daze

In this video I look at Commodore 64 "Skool Daze", noting how it uses a single screen bitmap mode, mostly software sprites with a few hardware sprites, and a very cool minimal dirty rectangle update for drawing the screen.
github.com/martinpiper/Debugg...
00:11 Introduction
00:20 Creating a prg from the tape version
11:59 Run it in C64DebugGUI, note sprites and graphics mode
14:51 Note the memory patterns, blobs align with software sprite positions
16:29 More hardware sprites for the speech bubble
17:42 ICU64 shows the same blobs for software sprites
20:09 Every bitmap cell draw
25:09 Stopping the render, understanding the logic
29:49 Game logic run four times, then renders
33:42 Finding dirty rectangle draw
37:20 Not all sprites are drawn each frame
38:07 Find the game state entity data

[@realsnoddas]

Love this deepdive into older games as their gamelogic is more unique than later games on c64, when the coders "stole" more from eachothers techniques as the code got more streamlined.

[@MartinPiper6502]

Thank you kindly :)

[@Sumaleth]

This is the sort of game that made me (wrongly) think software sprites were not suitable for fast arcade games on the C64. Flickery, low framerate, hires + color clash. Games like Fairlight, The Great Escape, and Head Over Heels too. Some great games there, but they all had those same sorts of limitations.

[@JohnMDiLiberto]

Thanks!

[@MartinPiper6502]

Wow thank you very much :)

[@NorthWay_no]

Are there any cartridge games that uses the VIC-II bank under the cart address space? That should be the "perfect" copy protection (as long as _all_ memory is used for something) and it would be interesting to see any game that does it and how it works.

[@MartinPiper6502]

As far as I know, no. The IO + colour RAM space at $d000 to $dfff is not mapped to cart. It can be CHARROM, IO or RAM.

[@alanbourke4069]

I wonder if you could get away with zone multiplexed hardware sprites instead, since they're pretty much segregated into the three floors of the school.

[@az09letters92]

C64 supports up to 8 sprites on same horizontal line. I counted at least 12 persons on a horizontal line, so not unless you'd alternate (or "blink") the remaining sprites or fall back to software sprites for the remaining objects.

[@VIC-20]

So it’s a speccy conversion?

[@MartinPiper6502]

Reading the disassembly, it does have a feel of code converted from Z80.