Introduction

In this project you’ll learn how to create a platform game, in which you have to dodge the moving balls and reach the end of the level.

Step 1: Character movement

Let’s start by creating a character that can move left and right, as well as climb up ladders.

Activity Checklist

  • Open the ‘Dodgeball’ Scratch project online at jumpto.cc/dodge-go or download from jumpto.cc/dodge-get and then open if you are using the offline editor.

    The project contains a background with platforms:

    screenshot
    screenshot
  • Add a new sprite, which will be your character. It’s better if you choose a sprite with multiple costumes, so that you can make it look as though it’s walking.

    screenshot
    screenshot
  • Let’s use the arrow keys to move your character around. When the player presses the right arrow, you want your character to point right, move a few steps and change to the next costume:

        when flag clicked
        forever
            if <key [right arrow v] pressed? > then
                point in direction (90 v)
                move (3) steps
                next costume
            end
        end
  • Test out your character by clicking the flag and then holding down the right arrow key. Does your player move to the right? Does your character look like they are walking?

    screenshot
    screenshot
  • To move your character to the left, you’ll need to add another if block inside your forever loop, which moves your character to the left.

  • Test your new code to make sure that it works. Does your character turn upside-down when walking to the left?

    screenshot
    screenshot

    If so, you can fix this bug by clicking the (i) icon on your character sprite, and then clicking the left-right arrow.

    screenshot
    screenshot

    Or, if you prefer you can add this block to the start of your character’s script:

    set rotation style [left-right v]
  • To climb a pink ladder, your character should move up slightly whenever the up arrow is pressed and they’re touching the correct colour. Add this code inside your character’s forever loop:

        if < <key [up arrow v] pressed?> and <touching color [#FF69B4]?> > then
            change y by (4)
        end
  • Test your character - can you climb the pink ladders and get to the end of your level?

    screenshot
    screenshot

Save your project

Challenge: Completing the level

Can you add more code to your character, so that they say something if they get to the green door?

screenshot
screenshot

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Step 2: Gravity and jumping

Let’s make your character move more realistically, by adding gravity and allowing them to jump.

Activity Checklist

  • You may have noticed that your character can walk off a platform into mid-air. Try to walk off of a platform and see what happens.

    screenshot
    screenshot
  • To fix this, let’s add gravity to your game. Create a new variable called gravity. You can hide this variable from your stage if you want to.

    screenshot
    screenshot
  • Add this new code block, which sets the gravity to a negative number, and then uses this to repeatedly change your character’s y-coordinate.

        when flag clicked
        set [gravity v] to [-4]
        forever
            change y by (gravity)
        end
  • Click the flag, and then drag your character to the top of the stage. What happens? Does the gravity work as you expected?

    screenshot
    screenshot
  • Gravity shouldn’t move your character through a platform or a ladder! Add an if block to your code, so that the gravity only works when your character is in mid-air. The gravity code should now look like this:

        when flag clicked
        set [gravity v] to [-4]
        forever
            if < not < <touching color [#0000FF]?> or <touching color [#FF69B4]?> > > then
                change y by (gravity)
            end
        end
  • Test the gravity again. Does your character stop when they are on a platform or a ladder? Can you walk off the edge of platforms to the level below?

    screenshot
    screenshot
  • Let’s also make your character jump when the player presses the space bar. One very easy way to do this is to move your character up a few times, using this code:

        when [space v] key pressed
        repeat (10)
            change y by (4)
        end

    As gravity is constantly pushing your character down by 4 pixels, you need to choose a number greater than 4 in your change y by (4) block. Change this number until you’re happy with the height your character jumps.

  • If you test out this code, you’ll notice that it works, but the movement isn’t very smooth. To make jumping look smoother, you’ll need to move your character by smaller and smaller amounts, until they’re not jumping anymore.

  • To do this, create another variable called jump height. Again, you can hide this variable if you prefer.

  • Delete the jumping code you added to your character, and replace it with this code:

        when [space v] key pressed
        set [jump height v] to [8]
        repeat until < (jump height) = [0] >
            change y by (jump height)
            change [jump height v] by (-0.5)
        end

    This code moves your character up by 8 pixels, then 7.5 pixels, then 7 pixels, and so on, until your character has finished jumping. This makes jumping look much smoother.

  • Change the starting value of your jump height variable and test it until you’re happy with the height your character jumps.

Save your project

Challenge: Improved jumping

Your character is able to jump whenever the spacebar is pressed, even if they’re already in mid-air. You can test this by just holding down the spacebar. Can you fix this, so that your character can only jump if they’re touching a blue platform?

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Step 3: Dodging balls

Now that you’ve got your character moving around, let’s add some balls for your character to avoid.

Activity Checklist

  • Create a new ball sprite. You can choose any type of ball you like.

    screenshot
    screenshot
  • Resize your ball, so that your character can jump over it. Try jumping over the ball to test it.

    screenshot
    screenshot
  • Add this code to your ball:

    screenshot
    screenshot

    This code creates a new ball clone every 3 seconds. Each new clone moves along the top platform.

  • Click the flag to test this out.

    screenshot
    screenshot
  • Add more code to your ball sprite, so that they move across all 3 platforms.

    screenshot
    screenshot
  • Finally, you’ll need code for when your character gets hit by a ball! Add this code to your ball sprite:

        when I start as a clone
        forever
            if < touching [Pico walking v]? > then
                broadcast [hit v]
            end
        end
  • You’ll also need to add code to your character, to move back to the start when they’re hit:

        when I receive [hit v]
        point in direction (90 v)
        go to x: (-210) y: (-120)
  • Test out your character and see if they go back to the start when they’ve been hit by a ball.

Save your project

Challenge: Random balls

The balls your character has to dodge all look the same, and always appear every 3 seconds. Can you improve them, so that they:

  • don’t all look the same?
  • appear after a random amount of time?
  • are a random size?
screenshot
screenshot

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Step 4: Lasers!

Let’s make your game a little harder to complete, by adding lasers!

Activity Checklist

  • Add a new sprite to your game, called ‘Laser’. It should have 2 costumes, called ‘on’ and ‘off’.

    screenshot
    screenshot
  • Place your new laser anywhere you like, between 2 platforms.

    screenshot
    screenshot
  • Add code to your laser, to make it switch between the 2 costumes.

        when flag clicked
        forever
            switch costume to [on v]
            wait (2) secs
            switch costume to [off v]
            wait (2) secs
        end

    If you prefer, you can wait a random amount of time between costume changes.

  • Finally, add code to your laser, so that the ‘hit’ message is broadcast when the laser touches your character. This code will be very similar to the code you added to your ball sprite.

    You don’t need to add any more code to your character - it already knows what to do when it is hit!

  • Test out your game to see if you can get past the laser. Change the wait times in your code if the lasers are too easy or too hard.

Challenge: More obstacles

If you think your game is still too easy, you can add more obstacles to your level. You can add anything you like, but here are some ideas:

  • A flying killer butterfly;
  • Platforms that appear and disappear;
  • Falling tennis balls that must be avoided.
screenshot
screenshot

You could even create more than one backdrop, and move to the next level when your character reaches the green door:

    if <touching color [#00FF00]?> then
        switch backdrop to [next backdrop v]
        go to x: (-210) y: (-120)
        wait (1) secs
    end

Save your project

Challenge: Improved gravity

There’s one other small bug in your game: gravity doesn’t pull your character downwards if any part of it is touching a blue platform - even its head! You can test this out by climbing most of the way up a ladder and then moving to the left.

screenshot
screenshot

Can you fix this bug? To do this, you need to give your character different coloured trousers (on all costumes)…

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screenshot

…and then replace the code:

    < touching color [#0000FF]? >

with:

    < color [#00FF00] is touching [#0000FF]? >

Remember to test your improvements to make sure you’ve fixed the bug!

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Challenge: More lives

Can you give your player 3 lives, instead of just sending them back to the beginning each time? Here’s how your game could work:

  • Your player starts with 3 lives;
  • Whenever your player gets hit, one life is lost and they go back to the start;
  • If there are no lives left, the game ends.

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