Somebody asked me what he can to improve in his mob arena map, I played his map and was unable to complete the first wave of monsters because the redstone made it so laggy... So I make an example map to show him how to make a map with minimal redstone activity and keep the quality of the map.

My plans for the map:
[done] Two seven segment displays for counting the waves
[in progress] A waves system that will spawn more monsters every time
- XP shop
[done] Items shop
- Classes
[in progress] Lots of strategies possible if you use your mind and creativity
- Challenge the player to get everything he need from basic stuff he can buy in the shops for XP or mob drops (including food, armor and weapons)
Goals:
- Not use any kind of clock.
- Make ALL the redstone devices to finish what they have to do in less than 5 seconds.

Suggestions and feedback are welcome!