Tuto tiny-ecs demo Part 8 Enemies

We continue with our tiny-ecs demo. It is time to add some "enemies".

Entity enemy1

First we create an entity of type enemy1.

In the entites folder "_E", create a file called "eNme1.lua" for example and copy the following code:

ENme1 = Core.class()

function ENme1:init(xspritelayer, x, y, dx, dy)
	-- ids
	self.isnme = true
	self.isactor = true
	-- sprite
	self.spritelayer = xspritelayer
	self.sprite = Pixel.new(math.random(0xffffff), 1, 32, 64)
	-- params
	self.x = x
	self.y = y
	self.health = 10
	-- BODY COMPONENT: function CBody:init(xspeed, xjumpspeed)
	self.body = CBody.new(4*16, 6*16) -- xspeed, xjumpspeed
	self.body.defaultmass = 1
	self.body.currmass = self.body.defaultmass
end

We start by adding some ids, a sprite layer and a sprite. The sprite here is a Pixel with a random color.

We add some more parameters like position and health.

Finally we add the body component so the entity can move.

Please note in the init parameters, there are two unused yet variables: dx and dy. They will be used when we add an artificial intelligence (AI) component later.

With ECS it is easy to build your game, you add/remove parameters and components as you need.

World addEntity

We need to add the enemy1 entity to tiny-ecs world. Let's add a couple of them.

Please go to the "LevelX.lua" file and complete the code as follow:

	...
	-- tiny-ecs
	self.tiny = require "classes/tiny-ecs"
	self.tiny.tworld = self.tiny.world()
	-- some enemies (xspritelayer, x, y, dx, dy)
	local nmes = {}
	for i = 1, 10 do -- we create 10 enemies
		nmes[i] = ENme1.new(self.camera, math.random(24)*16, 10*16, math.random(12)*16, 0)
		self.tiny.tworld:addEntity(nmes[i])
	end
	-- the player (xspritelayer, x, y)
	self.player1 = EPlayer1.new(self.camera, 12*16, 10*16)
	self.tiny.tworld:addEntity(self.player1)
	...

When we add an enemy1 entity to tiny-ecs world, we also add it to an nmes list so we can iterate through them in our game.

You can run the demo and you should see ten enemies placed randomly on the x axis.

Enemy add AI Component

Our enemy1 entities don't do anything yet. Let's equip them with an Artificial Intelligence component.

In the components folder "_C", create a file called "cAI.lua" for example, and copy the following code:

CAI = Core.class()

function CAI:init(x, y, dx, dy)
	self.startpositionx = x
	self.startpositiony = y
	self.dx = dx -- delta x
	self.dy = dy -- delta y
end

Here, in the init function, we store an entity starting position and a delta x and y to set how far it can travel.

We can now attach this AI component to our enemy1 entity in "eNme1.lua":

ENme1 = Core.class()

function ENme1:init(xspritelayer, x, y, dx, dy)
	-- ...
	self.health = 10
	-- BODY COMPONENT: function CBody:init(xspeed, xjumpspeed)
	self.body = CBody.new(4*16, 6*16) -- xspeed, xjumpspeed
	self.body.defaultmass = 1
	self.body.currmass = self.body.defaultmass
	-- AI COMPONENT: function CAI:init(x, y, dx, dy)
	self.ai = CAI.new(self.x, self.y, dx, dy)
	if self.ai.dx then self.isright = true end -- start moving our enemy1
	if self.ai.dy then self.isdown = true end -- start moving our enemy1
end

You can run the demo and the enemies should move to the right.

Enemy AI System

To make our enemies intelligent we need to create an AI system.

In the systems folder "_S", create a file called "sAI.lua" for example, and copy the following code:

SAI = Core.class()

function SAI:init(xtiny) -- tiny function
	xtiny.processingSystem(self) -- called once on init and every update
end

function SAI:filter(ent) -- tiny function
	return ent.ai
end

function SAI:onAdd(ent) -- tiny function
end

function SAI:onRemove(ent) -- tiny function
end

function SAI:process(ent, dt) -- tiny function
	if ent.ai.dx and ent.ai.dy then -- DIAGONAL
		if ent.x >= ent.ai.startpositionx + ent.ai.dx then
			ent.isleft, ent.isright = true, false
			ent.isup, ent.isdown = true, false
		elseif ent.x <= ent.ai.startpositionx then
			ent.isleft, ent.isright = false, true
			ent.isup, ent.isdown = false, true
		end
	elseif ent.ai.dx then -- HORIZONTAL
		if ent.x >= ent.ai.startpositionx + ent.ai.dx then
			ent.isleft, ent.isright = true, false
		elseif ent.x <= ent.ai.startpositionx then
			ent.isleft, ent.isright = false, true
		end
	elseif ent.ai.dy then -- VERTICAL
		if ent.y >= ent.ai.startpositiony + ent.ai.dy then
			ent.isup, ent.isdown = true, false
		elseif ent.y <= ent.ai.startpositiony then
			ent.isup, ent.isdown = false, true
		end
	end
end

This is a simple AI system, which switches an entity direction when it reaches some limits (delta x, delta y).

Finally we need to add this AI system to tiny-ecs world.

Please go to the "LevelX.lua" file and complete the code as follow:

	...
	-- the player (xspritelayer, x, y)
	self.player1 = EPlayer1.new(self.camera, 12*16, 10*16)
	self.tiny.tworld:addEntity(self.player1)
	-- add systems to tiny-ecs
	self.tiny.tworld:add(
		SDrawable.new(self.tiny),
		SDynamicBodies.new(self.tiny),
		SPlayer1Control.new(self.tiny),
		SAI.new(self.tiny)
	)
	...

You can run the demo and the enemies should be less dumb ;-)

Next?

In the next part, we make the player1 "shoots" and the enemies "die" :-(

Prev.: Tuto tiny-ecs demo Part 7 Systems to move actors
Next: Tuto tiny-ecs demo Part 9 Player Shoots Enemies Die

Tutorial - tiny-ecs demo

---

• Main Page
• Lua API
• Main API
• Plugins