Day 6: User Input & Conditionals

Work Session: Add Controls to Your Maze

Open the maze project you built last Friday. Today you will make it playable by adding keyboard controls.

If you lost your work, use this project.

Step 1: Add Keyboard Controls

Click on your player sprite and add these blocks. You need four when key pressed event blocks — one for each arrow key.

when [up arrow v] key pressed
change y by (10)

when [down arrow v] key pressed
change y by (-10)

when [left arrow v] key pressed
change x by (-10)

when [right arrow v] key pressed
change x by (10)

Step 2: Play Test

Click the green flag, then press the arrow keys. Your sprite should move around the stage.

• Can you navigate from start to finish?
• If the paths are too narrow or the sprite moves too fast, adjust your maze drawing or change the movement values (try 5 instead of 10).

Work Session: Bouncing Off Walls

Right now your sprite can walk straight through the walls. Let’s fix that using a conditional — a block that checks whether something is true and responds.

The if touching color Block

Scratch can detect when a sprite is touching a specific color on the stage. Since you drew all your maze walls in the same color, you can use this to detect wall collisions.

The if touching sprite Block

Scratch can also detect when a sprite is touching another sprite. Since our walls are a sprite, we can use this or the color option.

Step 1: Add Wall Detection

Add this code to your player sprite. It runs forever, constantly checking if the sprite is touching the wall color:

when green flag clicked
forever
if <touching color (#000000)?> then
go to x: (-200) y: (150)
end
end

Important: Click the color swatch in the touching color block, then use the eyedropper tool to pick the exact color of your maze walls.

Set the go to coordinates to your maze’s start position. To find the right numbers, drag your sprite to the start and look at the x and y values below the stage.

Step 2: Test It

Click the green flag and navigate the maze. When your sprite touches a wall, it should snap back to the start.

Challenge

Instead of going back to the start, try making the sprite undo its last move when it touches a wall. Hint: you’ll need to move the sprite in the opposite direction by the same amount.