add note on ecs_lookup and ecs_quit
@@ -238,3 +238,15 @@ The sooner you can let Flecs know what entities you will be setting on an entity
### Create entities in bulk
It is much more efficient to create entities in bulk (using the `ecs_new_w_count` function) than it is to create entities individually. When entities are created in bulk, memory for N entities is reserved in one operation, which is much faster than repeatedly calling `ecs_new`. What can provide an even bigger performance boost is that when entities are created in bulk with an initial set of components, the `EcsOnAdd` handler for initializing those components is called with an array that contains the new entities vs. for each entity individually. If your application heavily relies on `EcsOnAdd` systems to initialize data, bulk creation is the way to go!
+
+### Limit usage of ecs_lookup
+You can use `ecs_lookup` to find entities, components and systems that are named (that have the `EcsId` component). This operation is however not cheap, and you will want to limit the amount of times you call it in the main loop, and preferably avoid it alltogether. A better alternative to `ecs_lookup` is to specify entities in your system expression with the `ID` modifier, like so:
+
+```c
+ECS_SYSTEM(world, MySystem, EcsOnFrame, Position, ID.MyEntity);
+```
+
+This will lookup the entity in advance, instead of every time the system is invoked. Obtaining the entity from within the system can be done with the `ecs_column_entity` function.
+
+### Use ecs_quit to signal that your application needs to exit
+You can use `ecs_progress` to control the flow of your application, by running it in a while loop, and making the result of the function the condition of the while loop. This will keep your application running until you call `ecs_quit`. Using this pattern provides a common approach to signalling your application needs to exit across modules.
