(click to interact)(mouseover/click to play GIF)(spaceship graphic by Kenney)
Nowadays, most development tools provide ways of setting pivot/center point for imagery - that is, the relative point around which the image will rotate and usually be positioned relative to.
However, ability to define multiple pivot points per image remains relatively uncommon, despite being something that you want to have projectiles fire from a correct point of a sprite, display weapons/attachements at right relative points, or do anything else that demands relative offsets.
This post is about implementing custom timelines in GameMaker.
Admittedly, timelines remain to be one of the more dated features of the software, designed for a specific purpose and kept in their original form for compatibility.
Time to time you'll see someone stopping by on forums to write a big rant about how these are a mess, do not do what they expect them to do, and should be redesigned immediately.
People will usually also argue that doing these things by yourself is too hard.
Since it is far easier than people claim, I decided to write a post about this.