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Corona SDK

Create a Hundreds-Like Game - Adding Interaction

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This is the second installment in our Corona SDK Hundreds game tutorial. In today’s tutorial, we’ll add to our interface and the game interaction. Read on!


Where We Left Off. . .

Please be sure to check part 1 of the series to fully understand and prepare for this tutorial.


Step 1: Start Button Listeners

This function adds the necesary listeners to the TitleView buttons.

function startButtonListeners(action)
	if(action == 'add') then
		playBtn:addEventListener('tap', showGameView)
		creditsBtn:addEventListener('tap', showCredits)
	else
		playBtn:removeEventListener('tap', showGameView)
		creditsBtn:removeEventListener('tap', showCredits)
	end
end


Step 2: Show Credits

The credits screen is shown when the user taps the about button, a tap listener is added to the credits view to remove it.

function showCredits:tap(e)
	playBtn.isVisible = false
	creditsBtn.isVisible = false
	creditsView = display.newImage('credits.png', 0, display.contentHeight)
	
	lastY = titleBg.y
	lastX = titleBg.x
	transition.to(titleBg, {time = 300, y = (display.contentHeight * 0.5) - (titleBg.height + 20), x = (display.contentWidth * 0.5) - (titleBg.width * 0.5) - 10})
	transition.to(creditsView, {time = 300, y = (display.contentHeight * 0.5) + 35, onComplete = function() creditsView:addEventListener('tap', hideCredits) end})
end

Step 3: Hide Credits

When the credits screen is tapped, it'll be tweened out of the stage and removed.

function hideCredits:tap(e)
	transition.to(creditsView, {time = 300, y = display.contentHeight + 25, onComplete = function() creditsBtn.isVisible = true playBtn.isVisible = true creditsView:removeEventListener('tap', hideCredits) display.remove(creditsView) creditsView = nil end})
	transition.to(titleBg, {time = 300, y = lastY, x = lastX});
end

Step 4: Show Game View

When the Start button is tapped, the title view is tweened and removed revealing the game view. There are many parts involved in this view, so we'll split them in the next steps.

function showGameView:tap(e)
	transition.to(titleView, {time = 300, x = -titleView.height, onComplete = function() startButtonListeners('rmv') display.remove(titleView) titleView = nil end})

Step 5: Game Background

This code places the game background image in the stage.

-- Game Background
	
display.remove(bg)
gameBg = display.newImage('gameBg.png')

Step 6: Walls

Next we add the walls to the stage. They are created using the drawing API.

-- Walls
	
left = display.newLine(0, 240, 0, 720)
right = display.newLine(320, 240, 320, 720)
top = display.newLine(160, 0, 480, 0)
bottom = display.newLine(160, 480, 480, 480)

Step 7: Circles

This part creates five circles in the screen at a random position, the i variable is used to multiply a constant that will define the circles color making it lighter each time. A textfield is also created and both are held within a group to move them together.

-- Circles
	
circles = display.newGroup()
local color = 0
	
for i = 1, 5 do
	local rx = 21 + math.floor(math.random() * (display.contentWidth - 42))
	local ry = 21 + math.floor(math.random() * (display.contentHeight - 42))
		
	local cg = display.newCircle(rx, ry, 21)
	local label = display.newText('0',cg.x-4.2, cg.y-12.2, native.systemFontBold, 13)
	cg.fillColor = color + (i*40)
	cg:setFillColor(cg.fillColor)
	local c = display.newGroup(cg, label)
	c.pressed = false
	c.name = 'c'
	c.radius = 21

Step 8: Circle Physics

Here we add physics to our new circle.

	-- Circle Physics
		
	physics.addBody(c, 'dynamic', {radius = 21, bounce = 1})
	c:setLinearVelocity(100, 100)
		
	circles:insert(c)
end

Step 9: Wall Physics

And do the same with our walls.

-- Walls Physics
	
physics.addBody(left, 'static')
physics.addBody(right, 'static')
physics.addBody(top, 'static')
physics.addBody(bottom, 'static')

Step 10: Score TextField

Now we add the score textfields.

	-- Score TextField
	
	score = display.newText('0', 257, 4, native.systemFont, 15)
	score:setTextColor(150, 150, 150)
	local total = display.newText(' / 100', 267, 4, native.systemFont, 15)
	total:setTextColor(150, 150, 150)
	
	gameListeners('add')
end

Step 11: Game Listeners

This function adds the necessary listeners to start the game logic.

function gameListeners(action)
	if(action == 'add') then
		for i = 1, 5 do
			circles[i]:addEventListener('touch', onTouch)
			circles[i]:addEventListener('collision', onCollision)
		end
	else
		for i = 1, 5 do
			circles[i]:removeEventListener('touch', onTouch)
			circles[i]:removeEventListener('collision', onCollision)
		end
	end
end

Step 12: Increase Score

This code runs when the circle is touched.

First we increase the score.

function onTouch(e)
	if(e.phase == 'began') then
		e.target.pressed = true
		
		-- Increase Counter
	
		score.text = tostring(tonumber(score.text) + 2)

Step 13: Increase Size

Then the size of the circle. The circle will grow when the finger is no longer on it.

-- Increase size
		
e.target.radius = e.target.radius + 2

Step 14: Change Color

Changes the color from black/gray to red.

-- Change Color
	
e.target[1]:setFillColor(224, 11, 0)

Step 15: Update Circle

We recreate the circle and its properties when the touch event has ended.

	if(e.phase == 'ended') then
		e.target.pressed = false
		-- Update physics
		
		local number = tostring(tonumber(e.target[2].text)+2)
		local r = e.target.radius
		local cg = display.newCircle(e.target.x, e.target.y, r)
		local label = display.newText(number ,cg.x-4.2, cg.y-12.2, native.systemFontBold, 13)
		cg:setFillColor(e.target[1].fillColor)
		cg.fillColor = e.target[1].fillColor
		local c = display.newGroup(cg, label)
		c.pressed = false
		c.name = 'c'
		c.radius = r
		circles:remove(e.target)
		physics.addBody(c, 'dynamic', {radius = r, bounce = 1})
		c:setLinearVelocity(100, 100)
		c:addEventListener('touch', onTouch)
		c:addEventListener('collision', onCollision)
		circles:insert(c)
		
		-- Move Textfield when number is 2 digit
		if(tonumber(number) > 9) then
			label.x = label.x - 5
		end

Step 16: Level Complete

Here we check if the score has reached 100 points and call a win alert if true.

		-- Check if score has reached 100
		
		if(tonumber(score.text) >= 100) then
			local bg = display.newImage('gameBg.png')
			transition.from(bg, {time = 500, alpha = 0, onComplete = alert('win')})
		end
	end
end

Step 17: Collisions

The game is lost when a pressed circle collides with another one. The listeners are removed and a lost alert is called.

function onCollision(e)
	if(e.target.pressed and e.other.name == 'c') then
		-- Wait 0.1 seconds to stop physics
		timer.performWithDelay(100, function() physics.stop() end, 1)
		
		local r = e.target.radius
		local c = display.newCircle(e.target.x, e.target.y, r)
		c:setFillColor(224, 11, 0)
		
		gameListeners('rmv')
		transition.to(c, {time = 700, xScale = 25, yScale = 25, onComplete = alert('lost')})
	end
end

Step 18: Alert

The alert function displays a message according to the type of alert called.

function alert(action)
	if(action == 'win') then
		local alertView = display.newImage('won.png', 10, display.contentHeight * 0.5 - 41)
		transition.from(alertView, {time = 300, y = -82, delay = 500})
	else
		local alertView = display.newImage('lost.png', 10, display.contentHeight * 0.5 - 41)
		transition.from(alertView, {time = 300, y = -82, delay = 500})
	end
end

Step 19: Call Main Function

In order to start the game, the Main function needs to be called. With the above code in place, we'll do that here:

Main()

Step 20: Loading Screen

The Default.png file is an image that will be displayed right when you start the application while the iOS loads the basic data to show the Main Screen. Add this image to your project source folder, it will be automatically added by the Corona compliler.


Step 21: Icon

Using the graphics you created before you can now create a nice and good looking icon. The icon size for the non-retina iPhone icon is 57x57px, but the retina version is 114x114px and the iTunes store requires a 512x512px version. I suggest creating the 512x512 version first and then scaling down for the other sizes.

It doesn't need to have the rounded corners or the transparent glare, iTunes and the iPhone will do that for you.


Step 22: Testing in Simulator

It's time to do the final test. Open the Corona Simulator, browse to your project folder, and then click open. If everything works as expected, you are ready for the final step!


Step 23: Build

In the Corona Simulator go to File > Build and select your target device. Fill the required data and click build. Wait a few seconds and your app will be ready for device testing and/or submission for distribution!


Conclusion

Experiment with the final result and try to make your custom version of the game!

I hope you liked this tutorial series and find it helpful. Thank you for reading!

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