The Dink Network

Well, I figured out what I was doing wrong. I was testing it using editor sprites which, it turns out if you alter using scripting, also alters the "hard" field for the editor sprite which is then used by draw_hard_map for recalculation, rather than it just using the property for the corresponding live sprite, which in this case I was altering directly.

The main take-away from this is that live sprites created with scripts behave differently to live sprites derived from map sprites in some cases.