-- move any colliding Rects to make room for `a`
-- see https://akkartik.itch.io/carousel/devlog/649349/handling-cascading-collisions
move_others = function(a, depth)
	if depth == nil then depth = 0 end
	if depth > 10 then return end
--	print('move others', a.key)
	for _,d in pairs(Definitions) do
		if d ~= a then
			local msv = collide(a, d)
			if msv then
				move(d, msv)
				A1(d.key)
				move_others(d, depth+1)
			end
		end
	end
end