# Entity Component System ### Overview ECS is a way of writing code that provides high performance by default. Under the hood **coherence** is entirely ECS based but we supply the **coherence** Toolkit which is Mono-based to make it easier to make massive multiplayer games whatever way you want. {% hint style="info" %} The current version of **coherence** uses the Unity Entities package. Unity [recently announced ](https://forum.unity.com/threads/notice-on-dots-compatibility-with-unity-2021-1.1091800/#post-7029421)that they will not support this package in Unity 2021 for a while. This means that the current recommended Unity version for using **coherence** is Unity 2020 LTS. This is only temporary as we have been working on removing the reliance on Entities internally. {% endhint %} If you would like to use the **coherence** SDK without the toolkit, we would recommend you take some time to learn about ECS and DOTS (Data Orientated Tech Stack) with Unity. ### ECS has three principal parts: Entities — the entities, or things, that populate your game or program. Components — the data associated with your entities, but organized by the data itself rather than by entity. (This difference in organization is one of the key differences between an object-oriented and a data-oriented design.) Systems — the logic that transforms the component data from its current state to its next state— for example, a system might update the positions of all moving entities by their velocity times the time interval since the previous frame. Here are various materials to learn: * Unity DOTS Overview - * Unity ECS Documentation - * Unity Learn, ECS -