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.

tools/animator.hpp

@@ -66,8 +66,7 @@ namespace animator {
     void handle_keyboard_mouse();
     void render();
     bool active();
-    void run_animation();
-    void tick();
+    void update();
     void reload();
     void check_update();
     void change_form(int direction);