A small snake game

AhBadiane · March 2013

A small snake game

I want to create a small game of snake
The snake is composed of a header and 10 (or more) body members
Each part consists of a circle and covering slightly
The head (yellow) and will move the body (orange) should follow (see attach image)

I spent a lot of time on the examples supplied with Gideros and examples appcodingeasy.com Site

I analyzed:
b2.KINEMATIC_BODY: to have no gravity
b2.DistanceJoint: to keep the elements close
createFixture: I have more trouble
....

I'm sure the program (without moving) must take months to 100 lines, but I can not do

I need your help

thanhquan1512 · March 2013

If there is nothing to do with physics, I think I can made this without attached bodies.

1. Declare a snake Head circle. Declare others 9 circles, specify their position to form a snake, add these 9 pieces into a sprite group called grpSnakeBody

On ENTER_FRAME event:
1. Move Head by updating its position.
2. Loop through grpSnakeBody, update their movement according to its head.
3. Check if each of circle reach top edge of screen, then update it position to bottom edge, the same if it reach left edge then update its position to right edge.

On MOUSE_UP event:
4. Store event.x and event.y, store the current head position (headX, headY) then move the head to current event.x, event.y position
5. Move all snake body items to the event.x, event.y when ever they reach headX, headY

AhBadiane · March 2013

@thanhquan1512, I think the solution is not so simple because the snake has to follow a path a bit complicated, not just a translation as shown in the diagram below
I thought that would DistanceJoint the solution?

hgvyas123 · March 2013

@AhBadiane
not sure i am going to help you or going to make you more confuse

@all
i had made one small example

 
function drawArc(xc,yc,xradius,yradius,startAngle,endAngle,isFill)
	if yradius == nil then
		yradius = xradius
	end
	if startAngle == nil then
		startAngle = 0
	end
	if endAngle == nil then
		endAngle = 360
	end
	if isFill == nil then
		isFill = true
	end
	local shape = Shape.new()
	if isFill then
		shape:setFillStyle(Shape.SOLID, 0xffffff, 1)
	else
		shape:setLineStyle(3, 0x000000)
	end
	shape:beginPath()
	for i=startAngle,endAngle do
		if i==1 then
			shape:moveTo(math.sin(math.rad(i)) * xradius, math.cos(math.rad(i)) * yradius)
		else
			shape:lineTo(math.sin(math.rad(i)) * xradius, math.cos(math.rad(i)) * yradius)
		end
	end
	if isFill then
		shape:closePath()
	end
	shape:endPath()
	shape:setPosition(xc,yc)
	return shape
end
 
local  myCircle = {}
for i=1,10 do
	myCircle[i] = drawArc(300+20*i,200,10)
	stage:addChild(myCircle[i])
 
end
 
 
 
local function onEnterFrame()
	for i=10,2,-1 do
		myCircle[i]:setPosition(myCircle[i-1]:getPosition())
	end
 
	local x,y --speed variable
 
	if math.random(100) < 50 then
		x = 10
	else
		x = -10
	end
 
	if math.random(100) < 50 then
		y = 10
	else
		y = -10
	end
	myCircle[1]:setPosition(myCircle[1]:getX()+x,myCircle[1]:getY()+y)
end
stage:addEventListener(Event.ENTER_FRAME,onEnterFrame,stage)

it works perfectly [ yup i knows i am moving snake randomly and there is no control to handle it

] yuppy

but now the problem is how can i increase the speed of snake if i change my speed variable x and y to 20 there is a big space between each circle

any idea for this

AhBadiane · March 2013

Thank you @ hgvyas123
By changing the function onEnterFrame (), I should do it (avoid gaps or overlaps that gives a tiny snake)
But I remain convinced that the solution lies in http://appcodingeasy.com/Gideros-Mobile/Gideros-Box2d-Chains-and-Elastic-Ropes example, but the code is too complex for me

(

ar2rsawseen · March 2013

@AhBadiane do you need a simply draggable snake? Then yes it would be easier with box2d.

But if you want a traditional snake game, then there won't be much of a point from box2d, because you would have to update position of each cell manually (without box2d) in loop, to match position of previous cell, basically what @hgvyas123 did.

So what exactly do you want?

Scouser · March 2013

Similar to what @hgvyas123: is doing buy have a head circle and make the other pieces children of the head, then you only need to move the 1 object to start with.

function snake:init()
	local parent = stage
	self.myCircle = {}	-- The snake
	local circle
	local xp, yp = 100,300
	local rad = 10		-- radius
	self.rad = rad
	self.xp, self.yp = xp, yp
	self.dx = 0		-- movement delta x
	self.dy = -1		-- movement delta y moves snake up
	for i=1,10 do
		circle = self:drawArc(xp,yp,rad)		-- create a segment
		self.myCircle[i] = circle			-- add to our snake array
		parent:addChild(circle)			-- chain object to our parent object
		parent = circle					-- new parent object
		xp = -self.dx*rad*1.8
		yp = -self.dy*rad*1.8				-- Position relative to parent
	end
	self:addEventListener(Event.ENTER_FRAME,self.onEnterFrame,self)	
end
 
function snake:onEnterFrame(event)
	local nx = self.xp + self.dx	-- Next x position
	local ny = self.yp + self.dy	-- Next y position
	local rr = math.random(1000)	-- Random number
	local dir = 0
	if 	nx < self.rad or nx > (appWidth-self.rad) or
		ny < self.rad or ny > (appHeight-self.rad) or
		rr > 990 then		-- Must turn if at edge of screen or rand(1000)>990
		if rr > 995 then dir = 1
		else dir = 2 end
		if self.dx == 0 then
		-- Moving up/down so let's change to left/right
			if dir == 1 then 	-- turn right
				self.dx = self.dy
				self.dy = 0
			else
				self.dx = -self.dy
				self.dy = 0
			end
		else
			if dir == 1 then 	-- turn right
				self.dy = self.dx
				self.dx = 0
			else
				self.dy = -self.dx
				self.dx = 0
			end
		end
	end
 
	self.xp = self.xp + self.dx		-- Update new positions
	self.yp = self.yp + self.dy
	self.myCircle[1]:setPosition(self.xp, self.yp)
end

Extra code is required to check the segments of the snake and change their position relative only to their parent and again only one segment needs to change at a time.

Hope this helps

ar2rsawseen · March 2013

@Scousers @hgvyas123 so now it's a contest?
Moving snake in shortest possible code?

Scouser · March 2013

No contest, just my take on things.

Using @hgvyas123's method all segments have to be re-calculated every time.

Using my method only the head has to be recalculated unless the snake has changed direction then only one segment needs moving at a time until they are all going in the same direction.

AhBadiane · March 2013

Thx @Scouser, I will test your solution tomorrow
@ar2rsawseen, you ask the right question. My snake must control a ball in a breakout. It replaces the classic paddle

hgvyas123 · March 2013

ok no problem i accept that i had won

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