Corona SDK: Develop a Frenzic-like Game - Adding Interactivity

Welcome to the second post in our Corona SDK Frenzic-like game series. In today's tutorial, we'll be adding interactivity to our interface and coding the start of the game.

Where We Left Off. . .

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

Step 1: Declare Functions

Declare all functions as local at the start.


local Main = {}
local addTitleView = {}
local startButtonListeners = {}
local showCredits = {}
local hideCredits = {}
local destroyCredits = {}
local showGameView = {}
local destroyTitleView = {}
local addListeners = {}
local newBlock = {}
local timesUp = {}
local placeBlock = {}
local blockPlaced = {}
local complete = {}
local removeBlocks = {}
local alert = {}
local alertHandler = {}
local restart = {}

Step 2: Constructor

Next we'll create the function that will initialize all the game logic:

1
2	function Main()
3	addTitleView()
4	end

Step 3: Add Title View

Now we place the background and titleView in the stage.


function addTitleView()
	bg = display.newImage('bg.png')
	
	title = display.newImage('title.png')
	title.x = display.contentCenterX
	title.y = 100
	
	startB = display.newImage('startButton.png')
	startB.x = display.contentCenterX
	startB.y = display.contentCenterY
	startB.name = 'startB'
	
	creditsB = display.newImage('creditsButton.png')
	creditsB.x = display.contentCenterX
	creditsB.y = display.contentCenterY + 40
	creditsB.name = 'creditsB'
	
	titleView = display.newGroup()
	titleView:insert(title)
	titleView:insert(startB)
	titleView:insert(creditsB)
	
	startButtonListeners('add')
end

Step 4: Button Listeners

In this function we add the tap listeners to the buttons in the title view, this will take us to the game screen or the credits screen.


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

Step 5: Show Credits

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


function showCredits()
	credits = display.newImage('credits.png')
	transition.from(credits, {time = 300, x = bg.contentWidth * 2, transition = easing.outExpo})
	credits:addEventListener('tap', hideCredits)
	titleView.isVisible = false
end

Step 6: Hide Credits

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


function hideCredits()
	titleView.isVisible = true
	transition.to(credits, {time = 300, x = bg.contentWidth * 2, transition = easing.outExpo, onComplete = destroyCredits})
end

function destroyCredits()
	credits:removeEventListener('tap', hideCredits)
	display.remove(credits)
	credits = nil
end

Step 7: Add Game View

When the Start button is pressed, the title view is tweened and removed, revealing the game view.

1
2	function showGameView(e)
3	transition.to(titleView, {time = 300, y = -titleView.height, transition = easing.inExpo, onComplete = destroyTitleView})
4	end

Step 8: Remove the Title View

The title view is removed from memory and the game graphics are added to the stage.


function destroyTitleView()
	display.remove(titleView)
	titleView = nil
	
	-- Add GameView Graphics
	
	up = display.newImage('container.png')
	up:setReferencePoint(display.TopLeftReferencePoint)
	up.x = 125
	up.y = 100
	
	right = display.newImage('container.png')
	right:setReferencePoint(display.TopLeftReferencePoint)
	right.x = 230
	right.y = 205
	
	down = display.newImage('container.png')
	down:setReferencePoint(display.TopLeftReferencePoint)
	down.x = 125
	down.y = 310
	
	left = display.newImage('container.png')
	left:setReferencePoint(display.TopLeftReferencePoint)
	left.x = 20
	left.y = 205
	
	holder = display.newImage('container.png')
	holder:setReferencePoint(display.TopLeftReferencePoint)
	holder.x = 125
	holder.y = 205
	
	-- Lives & Score Text
	
	livesText = display.newText('Lives', 10, 10, 'Orbitron-Medium', 12)
	livesText:setTextColor(163, 255, 36)
	
	livesTF = display.newText('5', 24, 30, 'Orbitron-Medium', 12)
	livesTF:setTextColor(163, 255, 36)
	
	scoreText = display.newText('Score', 260, 10, 'Orbitron-Medium', 12)
	scoreText:setTextColor(163, 255, 36)
	
	scoreTF = display.newText('0', 274, 30, 'Orbitron-Medium', 12)
	scoreTF:setTextColor(163, 255, 36)
	
	gameView = display.newGroup()
	gameView:insert(up)
	gameView:insert(right)
	gameView:insert(down)
	gameView:insert(left)
	gameView:insert(holder)
	gameView:insert(livesText)
	gameView:insert(livesTF)
	gameView:insert(scoreText)
	gameView:insert(scoreTF)
	
	addListeners()
end

Step 9: Game Listeners

This function will add a Tap Listener to the square containers so you can tap them and place the current block in the center (holder) container.


function addListeners()
	up:addEventListener('tap', placeBlock)
	right:addEventListener('tap', placeBlock)
	down:addEventListener('tap', placeBlock)
	left:addEventListener('tap', placeBlock)
	
	lives = 5
	score = 0

Step 10: Container Variables

These variables are created inside the square containers, they are used to register the blocks, colors, and positions inside every square.

The letters represent the following positions:

a: top-left
b: top-right
c: bottom-left
d: bottom-right


-- Create a var for every container to determine when full
	
	up.blocks = 0
	right.blocks = 0
	down.blocks = 0
	left.blocks = 0
	
	-- Arrays used to remove blocks and detect color
	
	up.blocksGFX = {}
	right.blocksGFX = {}
	down.blocksGFX = {}
	left.blocksGFX = {}
	
	-- Create an boolean for every container to avoid placing blocks in the same position 
	
	up.a = false
	right.a = false
	down.a = false
	left.a = false 
	
	up.b = false
	right.b = false
	down.b = false
	left.b = false 
	
	up.c = false
	right.c = false
	down.c = false
	left.c = false 
	
	up.d = false
	right.d = false
	down.d = false
	left.d = false 
	
	-- Give a name to the containers to identify them later
	
	up.name = 'up'
	right.name = 'right'
	down.name = 'down'
	left.name = 'left'
	
	newBlock(true)
end

Step 11: Generate Random Block

This code picks a random block color from the Table, this will be used to instantiate the actual block. A parameter is used to determine if the timer needs to be started.


function newBlock(firstTime)
	-- New Block 
	
	local randomBlock = math.floor(math.random() * 3) + 1
	local block
	
	if(blockColor[randomBlock] == 'orange') then
		block = display.newImage('orangeBlock.png')
		block.name = 'orange'
		block:setReferencePoint(display.TopLeftReferencePoint)
	elseif(blockColor[randomBlock] == 'green') then
		block = display.newImage('greenBlock.png')
		block.name = 'green'
		block:setReferencePoint(display.TopLeftReferencePoint)
	elseif(blockColor[randomBlock] == 'purple') then
		block = display.newImage('purpleBlock.png')
		block.name = 'purple'
		block:setReferencePoint(display.TopLeftReferencePoint)
	end

Step 12: Add a New Block

After selecting the block color, the position where it will be placed its calculated using the positions table and then added to the blocks table and the stage.


currentXPosition = positions[math.floor(math.random() * 2) + 1]
	currentYPosition = positions[math.floor(math.random() * 2) + 1]
	
	block.x = holder.x + currentXPosition
	block.y = holder.y + currentYPosition
	table.insert(blocks, block)
	gameView:insert(block)

Step 13: Check Available Space

Before continuing with the game, we must check that the newly created block can actually be placed in a square container. The following code checks every container array to make sure that there is a position available to place the block. If not, the block is destroyed and the function is called again to generate another one.


local position = {currentXPosition, currentYPosition}
	
	if(position[1] == 5 and position[2] == 5 and up.a == true and right.a == true  and down.a == true  and left.a == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 35 and position[2] == 5 and up.b == true  and right.b == true  and down.b == true  and left.b == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 5 and position[2] == 35 and up.c == true  and right.c == true  and down.c == true  and left.c == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 35 and position[2] == 35 and up.d == true  and right.d == true  and down.d == true  and left.d == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	end

Step 14: Start Timer

The timer starts counting when the function is called for the first time.


if(firstTime) then
		-- Start Timer 	
		timerSource = timer.performWithDelay(3000, timesUp, 0)
	end
end

Step 15: Lives

Three seconds are given to place a block in a square container, if that time passes and the block is still in the center square, a life will be removed.


function timesUp:timer(e)
	-- Remove Life 
	
	lives = lives - 1
	livesTF.text = lives
	media.playEventSound('buzz.caf')

Step 16: Unused Blocks

After removing the life, the block in the center square will be destroyed and a new block will be generated.

1
2	display.remove(blocks[#blocks])
3	table.remove(blocks)

Step 17: Check for Game Over

This code checks if the player is out of lives and calls a function that will handle that.


	if(lives < 1) then
		alert()
	else
		-- Next Block 
		
		newBlock(false)
	end
end

Step 18: Code Review

Here is the full code written in this tutorial alongside with comments to help you identify each part:


-- Sort 'Frenzic' like Game
-- Developed by Carlos Yanez

-- Hide Status Bar

display.setStatusBar(display.HiddenStatusBar)

-- Graphics
-- [Background]

local bg

-- [Title View]
 
local title
local startB
local creditsB

-- [TitleView Group]

local titleView

-- [Score & Lives]

local livesText
local livesTF
local lives
local scoreText
local scoreTF
local score

-- [GameView]

local up
local right
local down
local left
local holder

--[GameView Group]

local gameView

-- [CreditsView]

local credits

-- Variables

local blockColor = {'orange', 'green', 'purple'}
local blocks = {}
local positions = {5, 35}
local currentXPosition
local currentYPosition
local eventTarget
local timerSource
local lives
local score
local bell
local bell4
local buzz

-- Functions

local Main = {}
local addTitleView = {}
local startButtonListeners = {}
local showCredits = {}
local hideCredits = {}
local destroyCredits = {}
local showGameView = {}
local destroyTitleView = {}
local addListeners = {}
local newBlock = {}
local timesUp = {}
local placeBlock = {}
local blockPlaced = {}
local complete = {}
local removeBlocks = {}
local alert = {}
local alertHandler = {}
local restart = {}

function Main()
	addTitleView()
end

function addTitleView()
	bg = display.newImage('bg.png')
	
	title = display.newImage('title.png')
	title.x = display.contentCenterX
	title.y = 100
	
	startB = display.newImage('startButton.png')
	startB.x = display.contentCenterX
	startB.y = display.contentCenterY
	startB.name = 'startB'
	
	creditsB = display.newImage('creditsButton.png')
	creditsB.x = display.contentCenterX
	creditsB.y = display.contentCenterY + 40
	creditsB.name = 'creditsB'
	
	titleView = display.newGroup()
	titleView:insert(title)
	titleView:insert(startB)
	titleView:insert(creditsB)
	
	startButtonListeners('add')
end

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

function showCredits()
	credits = display.newImage('credits.png')
	transition.from(credits, {time = 300, x = bg.contentWidth * 2, transition = easing.outExpo})
	credits:addEventListener('tap', hideCredits)
	titleView.isVisible = false
end

function hideCredits()
	titleView.isVisible = true
	transition.to(credits, {time = 300, x = bg.contentWidth * 2, transition = easing.outExpo, onComplete = destroyCredits})
end

function destroyCredits()
	credits:removeEventListener('tap', hideCredits)
	display.remove(credits)
	credits = nil
end

function showGameView(e)
	transition.to(titleView, {time = 300, y = -titleView.height, transition = easing.inExpo, onComplete = destroyTitleView})
end

function destroyTitleView()
	display.remove(titleView)
	titleView = nil
	
	-- Add GameView Graphics
	
	up = display.newImage('container.png')
	up:setReferencePoint(display.TopLeftReferencePoint)
	up.x = 125
	up.y = 100
	
	right = display.newImage('container.png')
	right:setReferencePoint(display.TopLeftReferencePoint)
	right.x = 230
	right.y = 205
	
	down = display.newImage('container.png')
	down:setReferencePoint(display.TopLeftReferencePoint)
	down.x = 125
	down.y = 310
	
	left = display.newImage('container.png')
	left:setReferencePoint(display.TopLeftReferencePoint)
	left.x = 20
	left.y = 205
	
	holder = display.newImage('container.png')
	holder:setReferencePoint(display.TopLeftReferencePoint)
	holder.x = 125
	holder.y = 205
	
	-- Lives & Score Text
	
	livesText = display.newText('Lives', 10, 10, 'Orbitron-Medium', 12)
	livesText:setTextColor(163, 255, 36)
	
	livesTF = display.newText('5', 24, 30, 'Orbitron-Medium', 12)
	livesTF:setTextColor(163, 255, 36)
	
	scoreText = display.newText('Score', 260, 10, 'Orbitron-Medium', 12)
	scoreText:setTextColor(163, 255, 36)
	
	scoreTF = display.newText('0', 274, 30, 'Orbitron-Medium', 12)
	scoreTF:setTextColor(163, 255, 36)
	
	gameView = display.newGroup()
	gameView:insert(up)
	gameView:insert(right)
	gameView:insert(down)
	gameView:insert(left)
	gameView:insert(holder)
	gameView:insert(livesText)
	gameView:insert(livesTF)
	gameView:insert(scoreText)
	gameView:insert(scoreTF)
	
	addListeners()
end

function addListeners()
	up:addEventListener('tap', placeBlock)
	right:addEventListener('tap', placeBlock)
	down:addEventListener('tap', placeBlock)
	left:addEventListener('tap', placeBlock)
	
	lives = 5
	score = 0
	
	-- Create a var for every container to determine when full
	
	up.blocks = 0
	right.blocks = 0
	down.blocks = 0
	left.blocks = 0
	
	-- Arrays used to remove blocks and detect color
	
	up.blocksGFX = {}
	right.blocksGFX = {}
	down.blocksGFX = {}
	left.blocksGFX = {}
	
	-- Create an boolean for every container to avoid placing blocks in the same position 
	
	up.a = false
	right.a = false
	down.a = false
	left.a = false 
	
	up.b = false
	right.b = false
	down.b = false
	left.b = false 
	
	up.c = false
	right.c = false
	down.c = false
	left.c = false 
	
	up.d = false
	right.d = false
	down.d = false
	left.d = false 
	
	-- Give a name to the containers to identify them later
	
	up.name = 'up'
	right.name = 'right'
	down.name = 'down'
	left.name = 'left'
	
	newBlock(true)
end

function newBlock(firstTime)
	-- New Block 
	
	local randomBlock = math.floor(math.random() * 3) + 1
	local block
	
	if(blockColor[randomBlock] == 'orange') then
		block = display.newImage('orangeBlock.png')
		block.name = 'orange'
		block:setReferencePoint(display.TopLeftReferencePoint)
	elseif(blockColor[randomBlock] == 'green') then
		block = display.newImage('greenBlock.png')
		block.name = 'green'
		block:setReferencePoint(display.TopLeftReferencePoint)
	elseif(blockColor[randomBlock] == 'purple') then
		block = display.newImage('purpleBlock.png')
		block.name = 'purple'
		block:setReferencePoint(display.TopLeftReferencePoint)
	end
	
	currentXPosition = positions[math.floor(math.random() * 2) + 1]
	currentYPosition = positions[math.floor(math.random() * 2) + 1]
	
	block.x = holder.x + currentXPosition
	block.y = holder.y + currentYPosition
	table.insert(blocks, block)
	gameView:insert(block)
	
	-- Check for an available space to move the block 
	
	local position = {currentXPosition, currentYPosition}
	
	if(position[1] == 5 and position[2] == 5 and up.a == true and right.a == true  and down.a == true  and left.a == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 35 and position[2] == 5 and up.b == true  and right.b == true  and down.b == true  and left.b == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 5 and position[2] == 35 and up.c == true  and right.c == true  and down.c == true  and left.c == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	elseif(position[1] == 35 and position[2] == 35 and up.d == true  and right.d == true  and down.d == true  and left.d == true ) then
		display.remove(block)
		block = nil
		newBlock(false)
	end
	
	-- Start Timer the first time the function is called 
	
	if(firstTime) then
		-- Start Timer 	
		timerSource = timer.performWithDelay(3000, timesUp, 0)
	end
end

function timesUp:timer(e)
	-- Remove Live 
	
	lives = lives - 1
	livesTF.text = lives
	media.playEventSound('buzz.caf')
	
	-- Remove Unused Block 
	
	display.remove(blocks[#blocks])
	table.remove(blocks)
	
	-- Check if out of lives 
	
	if(lives < 1) then
		--alert()
	else
		-- Next Block 
		
		newBlock(false)
	end
end

Next Time...

In the next and final part of the series, we'll handle the blocks behavior, scores, and the final steps to take prior to releasing the app -like app testing, creating a start screen, adding an icon, and building the app. Stay tuned for the final part!