Sorted out the animation vs. easing contradiction I believe. Now there's a separate easing_duration that's calculated from the total duration of all frames. Then a easing_position determines where in the total the animation is, which is fed to the asing functions as a ration of easing_position / easing_duration.

tests/animate2.cpp

@@ -22,7 +22,7 @@ Animate2 load_animation(const string& name) {
   anim.set_form("attack");
 
   anim.transform.looped = false;
-  anim.sequence.durations = {Random::milliseconds(5, 33), Random::milliseconds(5, 33)};
+  anim.sequence.durations = {Random::uniform(1, 5), Random::uniform(1, 5)};
   return anim;
 }