Unique Skeleton spawners

Instead of having every spawner be the same, I tried to make each one hqve a unique challenge. Starting with skeletons. The spawner and the skeletons would be in the middle of room while the player on one side, seperated by big gap with a a 20 block fall. The goal would be to make it to the other side while skeletons shoot at you. If you managed to dig straight into the middle, you would still have to be careful not to get hit off.