Inherited from naval wargaming, where it came about because first rate ships of the line had better armor than second rate etc. so armor class scaled inversely. That meant THAC0 was the best way to figure out what you needed to roll to get a hit.
It’s also not functionally that complicated (your THAC0 minus target AC), just weird and confusing if you try to understand why it works that way.
I can kind of get that, if they kept 1 as the hard cap on AC. But they have 0th rate as the reference point, and then bizarre instances of negative AC. A minus third rate ship reads like a dingier third rate ship, not better than a first class ship.
Inherited from naval wargaming, where it came about because first rate ships of the line had better armor than second rate etc. so armor class scaled inversely. That meant THAC0 was the best way to figure out what you needed to roll to get a hit.
It’s also not functionally that complicated (your THAC0 minus target AC), just weird and confusing if you try to understand why it works that way.
I can kind of get that, if they kept 1 as the hard cap on AC. But they have 0th rate as the reference point, and then bizarre instances of negative AC. A minus third rate ship reads like a dingier third rate ship, not better than a first class ship.