River trip

Introduction

This game involves the player in guiding a boat along a river which scrolls across the screen, trying
to avoid hitting the backs and obstacles such as logs which appear in the river.

List of techniques

• Painting Sprites
• Scrolling backgrounds
• Detecting when a Sprite touches a colour
• Forever loop
• If loops
• Using keyboard keys to move a Sprite
• Switching Sprite costumes after a collision
• Duplicating Scripts
• Score variable
• High Score variable
• Using a timer to terminate a game

Tutorial

	Our first job is to create the Sprites which will be scrolled acorss the Stage Area as the boat travels up the river. On loading the program, click on the Paint new sprite button above the Sprites List Area.
This will take you to the Paint Editor. Click a green colour for the banks of the river in the Colour Palette. Click the Zoom Out control button to the left of the canvas towards the bottom of the Paint Editor window. Click the Fill Bucket Tool in the Toolbox Move the Fill Bucket to the canvas and click to fill the entire canvas with green
	Click the Eraser Tool in the Toolbox Click the Eraser Size button in the Options Area beneath the Toolbox Click the largest size for the Eraser Tool Erase a wiggly line across the middle of the canvas. Try to ensure that the position of the erased area is roughly the same on each edge of the canvas as this will need to match up as the Sprite is scrolled across the Stage.
Click a light blueish colour for the water in the Colour Palette Click the Fill Bucket Tool in the Toolbox Click anywhere on the erased section of river on the canvas. Click the OK button to close the Paint Editor.
	We will now delete the Scratch the Cat Sprite (Sprite1). This could have been done earlier. Right-click (Ctrl-click on a Mac) the icon for the Scratch the Cat Sprite in the Sprites List Area Click delete in the pop-up menu
We will now create a Script to scroll the Sprite across the screen. Click the Control button above the Blocks Palette. From the Control Blocks Palette drag a when Green Flag clicked block into the Scripts Area Drag a Forever loop block from the Blocks Palette into the Script Area and attach it beneath the when Green Flag clicked block.
	Scroll down the Control Blocks Palette and then drag an If loop block into the Script Area and insert it into the Forever loop.
Click the Operators button above the Blocks Palette and from the Operators Blocks Palette, drag a diamond-shaped [ ] < [ ] block into the Script Area and insert it into the diamond-shaped pane in the header for the If loop block.
	Click the Motion button and from the Motion Blocks Palette, drag a set x to [0] block into the Script Area and insert it into the Script beneath the when Green Flag clicked block Now drag a set y to [0] block into the Script Area and attach it beneath the set x to [0] block. This ensures the river Sprite always goes to the centre of the Stage Area when the game starts.
Drag a move 10 steps block into the Script Area and insert it into the Forever loop above the If loop block.
	Change the value of the move block so it reads move -10 steps This will move the Sprite across the Stage Area from right to left rather than left to right.
Drag an x position block into the Script Area and insert it into the first pane of the [ ] < [ ] block in the header of the If loop block. Type -460 (ie minus460) into the second pane of the [ ] < [ ] block so the header of the If block now reads If x position < -460 This will detect when the Sprite reaches the left of the Stage Area.
	Now we must tell the Sprite what to do when it reaches the left edge of the Stage Area Drag a set x to 0 block into the Script Area and insert it into the If loop Change the value of the pane in this block so it now reads set x to 460 We are telling the Sprite to go to the right side of the Stage Area. If you now click the Green Flag button above the top right corner of the Stage Area you will see the effects of this script. Click the Red button beside the Green Flag button to stop the script.
As you can see, one background Sprite is not enough. We need another one to follow this Sprite across the Stage Area. The simplest way to create another Sprite similar to the this first one is to right-click (Ctrl-click on a Mac) the icon for the Sprite in the Sprite List Area and then click duplicate in the pop-up menu.
	This not only makes of copy of the Sprite, it also copies the Sprite's Script. Click on the new Sprite's icon in the Sprite List Area
In the Script Area for this new Sprite, change the first set x to 0 block if the Script so it reads set x to 470 This places this second Sprite on the extreme right of the Stage when the Green Flag button is pressed and then moves it across the screen, following the first Sprite. Click the Green Flag button above the Stage on the right to see how this works. If you feel the river looks a bit too uniform you could Edit the Costume for one of the Sprites to change the shape of the river section.
	We are now ready to create a Sprite for the boat. Click the Paint new Sprite button above the Sprite List Area Click a suitable colour for the boat (I've chosen brown) in the Colour Palette. Click the Circle tool in the Toolbox Draw an oval shape with the Circle Tool on the canvas. It doesn't matter what size it is for now as we can change the size later, if necessary.
With the paintbrush tool, add more details to your boat such as a pointed bow (to the right of the shape). Click Undo if you make a mistake. Click OK when you are happy with your boat.
	If you feel your boat is too large for the river, click the Shrink Sprite button and then click on the boat Sprite a few times until it is the right size You can enlarge it again if you become over-enthusiastic by clicking the Grow Sprite button beside the Shrink Sprite button and clicking on the Sprite. NOTE: Clicking anywhere outside the canvas will 'unclick'  the Shrink Sprite button
We now need to write a script to control the boat. Click the Control button above the Blocks Palette Area Drag a when [space] key clicked block into the Script Area and change the block to read when [up arrow] key pressed by selecting this from the drop-down menu
	Show the Motion blocks in the Blocks Palette by clicking the Motion button above the Blocks Palette Drag a point in direction [90] block into the Script Area and attach it to the when [up arrow] key pressed block Change the point in direction block so it reads point in direction [(0) up] by selecting this from the drop-down menu
Drag a move 10 steps block into the Script Area and attach it below the point in direction 0 block Test this new Script by pressing the up arrow key on the keyboard You can move the boat Sprite back down the Stage Area by dragging it with the mouse pointer
	We could go through the above procedure again to create a Script to move the boat Sprite down the screen, but a quicker way is to duplicate the up arrow script Right-click (Ctrl-click on a Mac) the when up arrow key pressed block and then select duplicate from the pop-up menu Note: if you right-click any other block in the Script it will only duplicate the part of the Script from that block downwards.
Change the new Script so it reads: when [down arrow] key pressed point in direction 180 (down) move 10 steps
	By selecting from the drop-down menus Test the new Script by pressing the up and down arrow keys on the keyboard You will notice however, that the boat Sprite rotates to point in the direction it is travelling which is not helpful.
To correct this rotation effect, click the Only face left-right button above the Script Area Test your handiwork by pressing the Green Flag button and then controlling the boat Sprite with the arrow keys
	We now need to check whether the boat remains in the river. Click the Control button and from the Control Blocks Palette, drag a when Green Flag clicked block into the Script Area for the boat Sprite. Now drag a forever loop block into the Script Area and attach it to the when Green Flag clicked block
Scroll down the Blocks Palette and then drag an If loop block into the Script Area and insert it into the Forever loop
	We need to insert a condition into the header of the If loop block to detect when the boat Sprite touches the banks of the river Click the Sensing button and from the Sensing Blocks Palette, drag a diamond-shaped touching colour _ ? block into the Script Area and insert it into the diamond-shaped pane in the header of the If loop block
Click the colour pane in the touching colour _? block and then click the eye-dropper tool on any part of the green colour in the Stage Area. This will set the touching colour _ ? block to detect when the sprite touches this colour.
	We need to create a new costume for the boat Sprite to show the effects of running into the bank. Click the Costumes tab above the Script Area and then click the Copy button This will create a copy of the original costume for the Sprite which we can now Edit. Click the Edit button for this new costume.
In the Paint Editor, use the paintbrush tool to show the boat in a crashed condition. Click the OK button when done.
	Click the Scripts tab to return to the Script Area
From the Looks Block Palette, drag a switch to costume [ ] block into the Forever loop between the header and the If loop block and, if necessary, change it to read switch to costume [costume1] Drag another switch to costume [ ] block and insert it into the If loop. If necessary, change it to read switch to costume [costume2]
	From the Control Blocks Palette, drag a wait 1 secs block and insert it into the If loop below the switch to costume [costume2] block Test the changes to the Script by pressing the Green Flag button and running the boat Sprite into the bank
We could do with adding some sort of scoring system. To do this we need a variable in which to store the score. Click the Variables button and then the Make a variable button. In the pop-up window type Score for the variable name and then click the OK button
	Drag a set Score to 0 block and insert it into the Green Flag Script immediately below the when Green Flag clicked block This will set the score to 0 each time the game is played.
To increase the score drag a change Score by 1 block and attach it below the when up arrow key pressed Script Attach another change Score by 1 block to the when down arrow key pressed Script If you now play the game by pressing the Green Flag button, you will see that the score increases each time you press the up or down arrow keys. The more the boat is moved by the player, the greater the score.
	We now need to decrease the score if the boat hits the bank Drag a change score by 1 block and insert it into the If loop. Change the block to read change Score by -10 Now play the game to see what happens if you hit the bank
To make the game more interesting, we will add a timer so players have to race against time to increase their score. Bring up the Sensing Blocks in the Blocks Palette by clicking the Sensing button. Click the checkbox beside timer to show this Variable in the Stage Area Now drag a reset timer block and insert it into the Green Flag Script beneath the when Green Flag clicked block. It doesn't matter if the reset timer block appears before or after the set Score to 0 block, as long as it comes before the Forever loop block
	To stop the game when the timer reaches 30 seconds we need to set up a condition in an If loop From the Control Blocks Palette, drag an If loop block and insert it into the Forever loop under the existing If loop. (You may need to try this a couple of times before you get the If loop block in the right place) Drag a stop all block into the new If loop
From the Operators Blocks Palette, drag a diamond-shaped [ ] > [ ] block and insert it into the diamond-shaped pane in the header of the new If loop block
	From the Sensing Blocks Palette, drag a timer block and insert it into the first pane of the [ ] > [ ] Operator block in the new If loop block Type 30 into the second pane of the greater than operator block so the If loop block header reads: If [timer] > [30] Test the game by pressing the Green Flag button
To make the game even more interesting, create a High Score variable and create another If loop inside the timer If loop which reads: If Score > High Score set High Score to Score
	Last of all, to make the game even more challenging, you could create a Sprite representing an obstacle floating down the river. As long as the object includes a patch of the same green colour as the river bank then the boat sprite will detect a collision with it The script for this obstacle I have suggested here hides this Sprite until the score exceeds 20.

Extensions

• Duplicate the obstacle sprite and change the script in the new obstacle so it appears when the score exceeds 50, say.
• Increase the variety of river shapes by adding two more costumes to the river bank sprites and include a random operator to choose the costume which is used when the sprite appears (eg switch to costume [random 1 to 3] )
• Increase the speed of the river sprites as the score increases

Pong

Introduction

This is a simplified version of the classic ping-pong game. The tutorial shows images from the downloadable version of Scratch (1.4) but the programming will work in the same way on the on-screen version Scratch (2.0)

Techniques included

The programming techniques which this game includes are:

• Drawing backgrounds
• Drawing sprites
• Importing sprites
• Green Flag scripts
• Key press scripts
• Sprite touching sprite detection
• Sprite touching colour detection
• Adding sound to sprites
• Updating score variable
• Updating High Score variable
• Changing sprite costume

Tutorial

Load up the program from either the website or using the download version. This is the start-up screen from Scratch 1.4 (the download version). The online version is similar but the various panes and and toolbars are in slightly different places. The online version includes some additional features which are not found in the download version - and so this tutorial will work with both versions.
	The first thing we will do is provide a background for our game. To change the design of the Stage (ie the background), click on the Stage icon in the Sprites Area
Notice that the heading for the Script Area shows you are now working on the Stage. Click on the Backgrounds tab and then the Edit button beside the thumbnail image of the Stage.
	The Paint Editor pop-up window will now appear. Select the colour required for the background (in our case green) from the Colour Palette, and then click on the Fill Bucket in the Toolbar. Now click somewhere on the canvas to fill it with the desired colour.
Next we need to add a line on the left of the Stage. We will need to protect this line from being touched by the ball. Click on white in the Colour Palette and then the Line Tool on the Toolbar. Change the line thickness by clicking in the Options Area (where it says Brush Size) and then selecting a middle-sized brush. Drag the line from top to bottom along the left side of the Canvas. Click OK to finish.
	Next we need to create a bat. Click on the button to Paint a New Sprite in the Sprites Area Sprites are objects which can be programmed with Scripts (see below)
This will take us once more to the Paint Editor. Click on the Line Tool on the Toolbar. Then select a middle-sized brush size from the Options Area. Drag a vertical line somewhere on the Canvas about the size shown here. Then click OK to exit the Paint Editor
	We could have done it earlier, but its now time to delete the default Sprite, Scratch the Cat. Right click (or Ctrl-click on a Mac) on the Sprite 1 (Scratch Cat) icon in the Sprites Area and then click on delete from the pop-up list. Alternatively you can Right Click (or Ctrl-click on a Mac) on the Sprite itself on the Stage Area.
Now drag the bat sprite (Sprite 2) which we have just created to the left of the Stage, just in front of the white line.
	We are now ready to start programming. Click the Control button to bring up the control blocks in the Blocks Palette. Drag the when 'space' key is pressed block from the Blocks Palette into the Script Area. This control block senses which key is being pressed on the keyboard and then carries out any instructions which are attached to it.
Click on the drop down menu on the block and click up arrow in the drop down list. This tells the control block to respond whenever the right arrow is pressed on the keyboard.
	Now we need to add some instructions to be carried out when the key is pressed. Click on the Motion button and then drag the point in direction 90 block into the Script Area and then drag it to just below the control block so that it attaches itself to that block. Now click on the drop-down menu and select (0) up from the list.This will tell the Sprite to face upwards so when it moves it will move up the screen.
Now drag the move 10 steps block from the Motion Blocks Palette and attach it to the point in direction block in the Script Area This instruction tells the Sprite to move 10 steps in whichever direction the Sprite is pointing.
	You can now test whether the instruction works by pressing the Up Arrow key on the keyboard. You will notice that the Sprite twists round to face in the upwards direction. This would be fine if it was a boat, an animal or a car, but we want our bat to keep facing forwards. To instruct the bat Sprite to continually face to the right, click the small only face left-right button in the pane above the Script Area Drag the Bat Sprite back down the screen and try pressing the Up Arrow key again
You can probably work out for yourself how to make another block which tells the Bat Sprite to move down the screen when the Down Arrow key is pressed - but to save time, we will use the existing Script by duplicating it. Right-click (Ctrl-click on a Mac) on the orange Control block at the top of the script we have just created and select duplicate from the pop-up menu
	Change the orange control block to read when down arrow key is pressed by choosing this option from the drop-down menu. Change the point in direction block to read point in direction (180) down. Now test your two Scripts by pressing the Up Arrow Key and Down Arrow Key to see if the Sprite moves up and down the screen. If not, check the blocks match those shown here.
Now we have programmed the bat to move up and down, we need something for it to hit. This time, instead of drawing our own ball, we will use an image from the Scratch program's library of image files. Click on the Choose new sprite from file button in the Sprites Area
	This will bring up the New Sprite Window. Double-Click on the Things folder.
Scroll down the list of images in the folder until you reach the tennisball image. Click on it and then click the OK button.
	You should now have the new tennis ball sprite showing on the Stage Area along with the bat sprite. However, it looks a bit too large so, to shrink it, click on the Shrink sprite button above the Stage Area.
Then keep clicking on the tennis ball sprite until it has shrunk to a reasonable size. If you feel you have overdone it, you can enlarge it by clicking the Grow Sprite button beside the Shrink Sprite button and then clicking a few times on the tennis ball sprite.
	Now we need to create a script to control how the ball sprite will move. Click on the Control button above the Blocks Palette and then from the Blocks Palette drag the when green flag clicked block into the Script Area and then drag the Forever loop block into the Script Area. Don't attach these two blocks together yet (it doesn't matter if you do though, you can always drag them apart again).
Now click the Motion button and then drag the point towards block into the Script Area and attach it below the when green flag clicked block. From the drop down menu on this block select Sprite 2. This tells the ball sprite that when the game starts it is to point towards the bat sprite before moving. This will make the game easier to play at the beginning. The drag the go to x: 0 y: 0 block into the Script Area and attach it beneath the point towards block. Change the value of x: to 200 by typing in the white area on this block. Drag the Move 10 steps block into the Script Area and put it into the Forever loop. Then change the move 10 steps to move 5 steps.
	Drag the if on edge bounce block from the Blocks Palette into the Script Area and attach it to the move 5 steps block in the Forever loop. The drag the Forever loop block and attach it to the go to x: 200 y:0 block You can now test the script controlling the ball sprite by clicking on the Green Flag button in the right hand corner above the Stage Area. The ball should first jump to the right of the stage ( ie x: 200, y: 0 co-ordinates) and then start moving across the stage towards the bat. When it reaches the edge of the stage area it will bounce and so-on until you press the Red button beside the Green flag button. This stops all scripts.
Our next job is to get the ball sprite to do something if it hits the bat sprite. From the Control Blocks Palette, drag the If loop block into the Script Area. You may need to scroll down the Block Palette Area to find the If loop block as it is somewhere near the bottom.
	Click on the Sensing button to bring up the Sensing Blocks in the Blocks Palette Area. Drag the diamond shaped touching _ ? block into the diamond shaped area at the top of the If loop in the Script Area. The click the drop down list button on the touching _? block and select Sprite 2. This tells the ball sprite that it will need to do whatever is contained inside the If loop if it touches the bat sprite (ie Sprite 2).
We now need to program the instructions inside the If loop. Click on the Motion button and from the Motion Blocks Palette, drag the point in direction 90 block into the Script Area and put it inside the If loop.
	As we want the ball to bounce off the bat in the opposite direction to that in which it was travelling when it hit the bat, we need to do a quick calculation as to what the new direction will be. Click the Operators button and from the Operators Block Palette drag the oval shaped _ - _ block into the oval shaped pane on the point in direction _ block in the If loop in the Script Area.
To find out the direction the ball sprite is heading when it strikes the bat sprite, firstly type 360 into the first pane of the point in direction _ - _ block in the If loop. Then bring up the Motion Blocks Palette by clicking the Motion button and from this drag the direction block into second pane of the the point in direction 360 - _ block This tells the ball sprite that it needs to point in the opposite direction when it strikes the bat sprite (ie 360 degrees minus the direction it is now travelling).
	Drag the If loop into the Forever loop so it attaches below the if on edge bounce block. Drag the Forever loop up and attach it to the blocks below the when green flag clicked block. The script for the ball sprite should now look like this. You can test this new script by clicking the green flag button and watching what happens when the ball hits the bat. When you are ready, stop all scripts by clicking the big red button beside the green flag button.
Now, let's add a sound when the bat hits the ball. Click on the Sounds tab above the Script Area for the ball sprite. The click on the Import button (or you could record your own sound if you prefer). In the Import Sound pop-up window, double-click the Effects folder and from from this select the Pop file and click OK.
	Click the Sound button above the Blocks Palette Area and drag the play sound Pop block into the Script Area and insert it into the If loop. It doesn't matter if it attaches itself above or below the point in direction block as long as it is inside the loop (it doesn't matter if the pop sound comes before or after the ball sprite changes direction). Click the Green Flag button to check this change to the script. Click the Red button to stop all scripts when you are ready
Now we have programmed the sprites to do what we want, it's time to add some means of presenting this player with a score. For this we will need a variable called Score. Click the Variables button above the Blocks Palette Area. Then click the Make a Variable button In the Pop-up window type Score for the variable name and then click the OK button.
	You will see that the Score variable is displayed as a counter in the Stage Area. This can be removed by clicking the checkbox beside the Score variable block in the Blocks Palette Area Drag set Score to 0 block from the Blocks Palette into the Script Area and attach it to the existing script under the go to x: 200 y: 0 block Drag the change Score by 1 block from the Blocks Palette Area into If loop in the script (again it doesn't matter where as long as it is inside the loop). You can check the effect of this change by clicking the Green Flag button to play the game and then the Red button to stop playing.
We now need to detect when we have missed hitting the ball. Firstly, click the Control button and drag a new If loop into the Script Area from the Control Block Palette Area. For now do not attach it to the script. Click the Sensing button and from the Sensing Control Block Palette, drag the touching colour _ ? block into the space at the top of the If loop block.
	This If loop is going to detect whether the ball sprite touches the white line behind the bat sprite (ie if the bat has missed hitting the ball). To ensure that the colour which the If loop detects is accurate, click in the colour pane in the touching colour _ ? block in the If loop block and then click on the white line on the Stage Area with the eye dropper mouse-pointer.
Import the BellToll sound file into the Sounds part of the Script Area (as above) - or any other sound which you think is appropriate. Click the Sound button and then drag the play sound BellToll until done block from the Sound Block Palette into the new If loop in the Script Area. Click the Control button and drag the  Stop All block from the Block Palette into the If loop so it comes after the play sound BellToll until done block. It is important that these are in the correct order otherwise the script will stop before the sound has played.
	Drag the new If loop into the Forever loop into the when Green Flag clicked script as shown. As it is inside the Forever loop the script will keep checking whether the ball sprite is touching the white line as long as the game is being played. You can now play the game by clicking the Green Flag button to see what happens if you miss the ball.
Next, it would be useful to record the Highest score and see if you can beat it it each time you play. This will require another If loop in the script. This time we will need to drag the Greater Than Operator block into the space in the header for the If loop.
	Make a new variable called High Score and then drag the blocks into the If loop to make the following statement: If Score > High score set High Score to Score
This new If loop should now be dragged inside the If touching colour _? loop in the script (as shown). It would still work outside this loop but the High Score is usually updated at the end of the game rather than during the game. You could also drag the Score and High Score displays in the Stage Area so they do not hide the top of the screen where the bat needs to hit the ball.
	Finally, to make the game more difficult for those who become skilful, let's make the bat smaller if they get a score higher than 15. Click on the button for the bat sprite (Sprite 2) in the Sprite Area. Then click on the Costumes tab Click on the Paint button beside the New costume label. In the Paint Editor window, draw a shorter bat than the first one and then click OK
In the Script Area for the bat sprite, using your knowledge of  programming create a new script: When Green Flag clicked Forever If High Score > 15 switch to costume costume 2 as shown  Note: the switch to costume block is in the Looks Blocks Palette

Extensions 

 To extend the game further you could:

• Increase the speed of the ball as the high score increases
• Add another bat so the game becomes a two-player game
• Add a random element to the direction in which the ball bounces off the bat