gt: 						btnBack.getPosition().x - btnBack.getRadius(), 
context: package com.not.itproject.screens;
  
  import com.badlogic.gdx.Gdx;
  import com.badlogic.gdx.graphics.Color;
  import com.badlogic.gdx.graphics.GL20;
  import com.badlogic.gdx.graphics.g2d.TextureRegion;
  import com.badlogic.gdx.graphics.glutils.ShapeRenderer.ShapeType;
  import com.badlogic.gdx.math.Vector2;
  import com.not.itproject.handlers.AssetHandler;
  import com.not.itproject.objects.SimpleButton;
  import com.not.itproject.objects.SimpleRoundButton;
  import com.not.itproject.zero.ProjectZero;
  
  public class HelpScreen extends AbstractScreen {
  	// declare variables
  	SimpleButton btnPrevious;
  	SimpleButton btnNext;
  	SimpleButton btnClose;
  	SimpleRoundButton btnBack;
  	HelpState screenStatus;
  	
  	// determines number of help screens
  	private static final int NUM_HELP_PAGES = 3;
  	enum HelpState { HELP_ONE, HELP_TWO, HELP_THREE };
  	
  	// main constructor
  	public HelpScreen(ProjectZero game) {
  		// define super
  		super(game);
  		
  		// initialise variables
  		screenStatus = HelpState.HELP_ONE;
  		
  		int btnWidth = 100; // assign for main buttons
  		btnPrevious = new SimpleButton((int)(gameWidth * 1/4) - btnWidth/2, 
  				(int)(gameHeight * 4/5), btnWidth, 30);
  		btnNext = new SimpleButton((int)(gameWidth * 3/4) - btnWidth/2, 
  				(int)(gameHeight * 4/5), btnWidth, 30);
  		btnBack = new SimpleRoundButton(20, 20, 15);
  	}
  	
  	// functions to determine the page status and its page number
  	private int determineHelpPageNumber(HelpState state) {
  		switch (state) {
  			case HELP_ONE:		return 1;
  			case HELP_TWO:		return 2;
  			case HELP_THREE:	return 3;
  			default:			return 0;
  		}
  	}
  	
  	private HelpState determineHelpPageStatus(int pageNumber) {
  		switch (pageNumber) {
  			case 1:		return HelpState.HELP_ONE;
  			case 2:		return HelpState.HELP_TWO;
  			case 3:		return HelpState.HELP_THREE;
  		}
  		return screenStatus;
  	}
  	
  	// functions to proceed to previous/next help pages
  	private void previousHelpPage() {
  		int currentPageNumber = determineHelpPageNumber(screenStatus);
  		if (currentPageNumber > 1 && currentPageNumber <= NUM_HELP_PAGES) {
  			// go to previous page
  			screenStatus = determineHelpPageStatus(currentPageNumber - 1);
  		}
  	}
  	
  	private void nextHelpPage() {
  		int currentPageNumber = determineHelpPageNumber(screenStatus);
  		if (currentPageNumber >= 1 && currentPageNumber < NUM_HELP_PAGES) {
  			// go to next page
  			screenStatus = determineHelpPageStatus(currentPageNumber + 1);
  		}
  	}
  
  	public void update(float delta) {		
  		// update objects
  		btnPrevious.update(delta);
  		btnNext.update(delta);
  		btnBack.update(delta);
  		
  		// check input from user and perform action
  		if (btnBack.isTouched()) {
  			game.nextScreen(ProjectZero.mainScreen, this);
  			// debug log to console
  			ProjectZero.log("Back button is pressed.");
  			
  		}
  		
  		// determine screen status
  		switch (screenStatus) {
  			case HELP_ONE:
  				// check input from user and perform action
  				if (btnNext.isTouched()) {
  					nextHelpPage();
  					// debug log to console
  					ProjectZero.log("Next page button is pressed.");
  					
  					
  				}
  				break;
  				
  			case HELP_TWO:
  				// check input from user and perform action
  				if (btnPrevious.isTouched()) {
  					previousHelpPage();
  					// debug log to console
  					ProjectZero.log("Previous page button is pressed.");
  					
  				} else if (btnNext.isTouched()) {
  					nextHelpPage();
  					// debug log to console
  					ProjectZero.log("Next page button is pressed.");
  					
  				}
  				break;
  				
  			case HELP_THREE:
  				// check input from user and perform action
  				if (btnPrevious.isTouched()) {
  					previousHelpPage();
  					// debug log to console
  					ProjectZero.log("Previous page button is pressed.");
  					
  				}
  				break;
  		}
  	}
  	
  	@Override
  	public void render(float delta) {
  //		// clear screen
  //		Gdx.graphics.getGL20().glClearColor(0.65f, 1f, 0.85f, 0.85f);
  //		Gdx.graphics.getGL20().glClear(GL20.GL_COLOR_BUFFER_BIT);
  		
  		// update objects
  		update(delta);
  
  		// determine screen status
  		switch (screenStatus) {
  			case HELP_ONE:
  				// clear screen
  				Gdx.graphics.getGL20().glClearColor(0.65f, 0.7f, 0.85f, 0.85f);
  				Gdx.graphics.getGL20().glClear(GL20.GL_COLOR_BUFFER_BIT);
  				
  				// render first help screen
  				batch.begin();
  				
  				// draw background
  				batch.draw(AssetHandler.backgroundUniversal, 0, 0,
  						gameWidth, gameHeight);
  				
  				batch.draw(AssetHandler.helpSessions, 0, 0,
  						gameWidth, gameHeight);
  				batch.draw(AssetHandler.buttonBack, 
  						btnBack.getPosition().x - btnBack.getRadius(), 
  						btnBack.getPosition().y - btnBack.getRadius(), 
  						btnBack.getRadius() * 2, btnBack.getRadius() * 2);
  				batch.draw(AssetHandler.buttonNavigateNext, 
  						btnNext.getPosition().x, 
  						btnNext.getPosition().y, 
  						btnNext.getWidth(), btnNext.getHeight());
  				batch.end();
  				break;
  				
  			case HELP_TWO:
  				// clear screen
  				Gdx.graphics.getGL20().glClearColor(0.65f, 0.8f, 0.85f, 0.85f);
  				Gdx.graphics.getGL20().glClear(GL20.GL_COLOR_BUFFER_BIT);
  				
  				// render second help screen
  				batch.begin();
  				
  				// draw background
  				batch.draw(AssetHandler.backgroundUniversal, 0, 0,
  						gameWidth, gameHeight);
  				
  				batch.draw(AssetHandler.helpTrackSelection, 0, 0,
  						gameWidth, gameHeight);
  				batch.draw(AssetHandler.buttonBack, 
  						btnBack.getPosition().x - btnBack.getRadius(), 
  						btnBack.getPosition().y - btnBack.getRadius(), 
  						btnBack.getRadius() * 2, btnBack.getRadius() * 2);
  				batch.draw(AssetHandler.buttonNavigatePrev, 
  						btnPrevious.getPosition().x, 
  						btnPrevious.getPosition().y, 
  						btnPrevious.getWidth(), btnPrevious.getHeight());
  				batch.draw(AssetHandler.buttonNavigateNext, 
  						btnNext.getPosition().x, 
  						btnNext.getPosition().y, 
  						btnNext.getWidth(), btnNext.getHeight());
  				batch.end();
  				break;
  				
  			case HELP_THREE:
  				// clear screen
  				Gdx.graphics.getGL20().glClearColor(0.65f, 0.9f, 0.85f, 0.85f);
  				Gdx.graphics.getGL20().glClear(GL20.GL_COLOR_BUFFER_BIT);
  				
  				// render second help screen
  				batch.begin();
  				
  				// draw background
  				batch.draw(AssetHandler.backgroundUniversal, 0, 0,
  						gameWidth, gameHeight);
  				
  				batch.draw(AssetHandler.helpGameplay, 0, 0,
  						gameWidth, gameHeight);
  				batch.draw(AssetHandler.buttonBack, 
  