Option 2

local Dir = {
	[Direction.UP] = Vector(0,-1),
	[Direction.DOWN] = Vector(0,1),
	[Direction.LEFT] = Vector(-1,0),
	[Direction.RIGHT] = Vector(1,0)
}

function ArunesMod:OnUpdate(player)
    local MoveDir = player:GetMovementDirection()
    for _, entities in pairs(Isaac.GetRoomEntities()) do
        if entities.Type == EntityType.ENTITY_EFFECT
        and entities.Variant == EffectVariant.YOUR_COSTUME_EFFECT then
            local costumeEffect = entities
            local sprite = costumeEffect:GetSprite()
            -- check the fire direction to set the offset
			if MoveDir == Direction.DOWN then
				if not (sprite;IsPlaying(“WalkDown“ then
                    sprite:Play(“WalkDown“, true)
                end
			elseif MoveDir == Direction.RIGHT then
				if not (sprite;IsPlaying(“WalkRight“ then
                    sprite:Play(“WalkRight“, true)
                end
			elseif MoveDir == Direction.UP then
				if not (sprite;IsPlaying(“WalkUp“ then
                    sprite:Play(“WalkUp“, true)
                end
			elseif MoveDir == Direction.LEFT then
				if not (sprite;IsPlaying(“WalkLeft“ then
                    sprite:Play(“WalkLeft“, true)
                end
			end
        end
    end
end