Prod snowballs when they are stuck

src/snowball.lua

@@ -137,14 +137,32 @@ function snow_snowball_ENTITY.on_step(self, dtime)
 	end
 
 	if self.physical then
-		local fell = self.object:getvelocity().y == 0
+		local vel = self.object:getvelocity()
+		local fell = vel.y == 0
 		if not fell then
+			if self.probably_stuck then
+				self.probably_stuck = nil
+			end
+			return
+		end
+		if self.probably_stuck
+		and vel.x == 0
+		and vel.z == 0 then
+			-- add a small velocity to move it from the corner
+			vel.x = math.random() - 0.5
+			vel.z = math.random() - 0.5
+			self.object:set_velocity(vel)
+			self.probably_stuck = nil
 			return
 		end
 		local pos = vector.round(self.object:getpos())
 		if minetest.get_node(pos).name == "air" then
 			pos.y = pos.y-1
 			if minetest.get_node(pos).name == "air" then
+				if vel.x == 0
+				and vel.z == 0 then
+					self.probably_stuck = true
+				end
 				return
 			end
 		end