diff --git a/Colliders.md b/Colliders.md
index 154d9af..b7cd0b2 100644
--- a/Colliders.md
+++ b/Colliders.md
@@ -9,6 +9,13 @@ wears already is greyed out. Colliders can be reused across objects that way, ov
 instance and stacked (hitbox + hurtbox on one sprite; colliders of the same body never collide
 with each other).
 
+On a sprite whose picture is a frame with a collision outline, the new collider is a
+[Frame collision](#shapes) of that frame instead of a box (#218). It reads the frame the sprite
+shows at that moment, an animation changing the frame later does not change the collider. A sprite
+drawn bigger or smaller than the frame gets the collider's *Scale* set so the outline covers the
+picture. A sprite stretched out of the frame's proportions keeps the box, because an outline
+cannot be stretched; so does a frame without an outline, a whole texture or vector art.
+
 **Fit to sprite** (#222) in the menu of a placed collider sizes it like the sprite it sits on and
 centres it there — handy after the sprite changed size or the collider was dragged aside. The size
 goes into this placement's overrides, so other sprites wearing the same collider keep theirs; a
diff --git a/Development.md b/Development.md
index ee3f0be..65367c9 100644
--- a/Development.md
+++ b/Development.md
@@ -18,7 +18,7 @@ php tests/php/accounts.test.php                               # the API's accoun
                                                               #   has and the web server's container has not (SKIP there)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1616 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1617 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result