Longbow arrow stops in mid-air
From Worms Knowledge Base
"The longbow has very weird mechanics. Its collision mask is a single pixel, but every frame it checks against the arrow mask. So, it can either collide due to its arrow mask, or the pixels in between the gaps.
If it's the pixel mask that collides, the arrow doesn't instantly stop. It waits until the next frame to stop and embed itself. However, if it's the arrow mask that collides, then it instantly stops because it's already at a frame boundary.
I probably could have explained that better, but this picture should help. Notice that occasionally, the green pixels poke out from behind the longbow arrow mask. That is where this weird kind of collision can happen:"