Entities

• Games usually consist of entities
  • In Godot, they are Nodes - in Unity, they are called GameObjects
• In TIC-80, we need to create some sort of entity system ourselves.
• Lua's tables can serve as entities
• We don't need classes from object-oriented programming, but the concept of wrapping entity data inside an object (or in our case, a Lua table) is helpful

Entity skeleton

entity={
    x=0,y=0,
    w=8,h=8,
    init=function(ent)
        to(entities,ent)
    end,
    upd=function(ent)
        ...
    end,
    drw=function(ent)
        ...
    end,
}
entity:init()--add the one entity to the entity table

Entity insides

• Above, we have an empty entity with position (x, y), width and height (w, h), and three functions
  • init is called when the entity is initialized
    • We add the entity to the global entities table here
  • upd is used to update the entity
    • Change position, calculate collision, etc.
  • drw is used to draw the entity.
• All these functions take in one argument: The table itself.

Main loop

• With these entities, we can create a simple main loop

  function TIC()
      for i,ent in ipairs(entities)do--update all entities
          ent:upd()
      end
      for i,ent in ipairs(entities)do--draw all entities
          ent:drw()
      end
  end
  

Create multiple entities easily

• If you want to create easily multiple entities (like enemies, bullets, etc), create a function where you can do that:

  function newEntity()
      local entity={
          x=0,y=0,
          w=8,h=8,
          init=function(ent)
              to(entities,ent)
          end,
          upd=function(ent)
              ...
          end,
          drw=function(ent)
              ...
          end,
      }
      entity:init()
  end
  

Spawn entities based on specific tiles on the map

• WIP