What are we going to learn this week…

• How to imitate a Button
• How to use the Pen controls
• How to use sliders

Buttons.

 Wouldn’t it be great if you could have buttons in Scratch, that you can click and make things happen?

Well you can, there might not be a code block to do it, but we can make one.

 You will need a Sprite with Two Costumes

• One for the Up position
• One for the Down Position

See how I have given the Sprite a meaningful name and also each costume has a name. The only difference between the sprites is the bottom one has no shadow and is slightly lower and left (covering the shadow).

Cool Tip: You can export the Button Sprite which will save it with all the code as well. This means it is easy to add Buttons to any other Scratch Projects. 

Crazy Images.

We are going to use the Pen Tool to draw some fancy Spirograph like images.

First we need a Sprite that will do the drawing, I just created an invisible Sprite, so you only see the Line being drawn.

Spirographs work using circles, but we are going to use triangles, squares, pentagons, hexagons and heptagons (7 sided).

If you walk 10 steps turn 90 degrees and walk another 10 steps and again and again, you have wlaked in a square, but if you change either how many steps or the angle you turn by a very SMALL amount and just keep[ going you can generate some very interesting patterns.

Sliders.

We will also be using sliders to control the nember of sides to the shape and the change in angles.

Sliders are variables that are displayed on the screen with a slider control to change the value as the program is running. To get the variable to show as a Slider just dbl click on it, once, changes it to a Slider, dbl clicking again, removes the name.

If you right click on the SLider you can set Min and Max values.

The code to create the Spirals is split into two parts. One runs when youclick the Green Flag, this just sets everything up ready.

The next piece of code is what does all the work, notice where the Slider variables are used and how the code makes more sense when you give variables descriptive names.

Movies are lots of single pictures shown very quickly one after the other.

Most movies run at 24 pictures a second!!

We can do the same in Scratch.

Question: If there are 24 pictures in one second, how long is each picture shown for?

Answer: in 100th of a second please…

You should have come up with something like this…

1 / 24 = 0.042

And we can code this in scratch like this:

And to keep things nice and neat, we can use a Broadcast to tell the Sprite to move

Now you don’t need to change this code anymore…

So what kind of Sprite  are we going to have and how will it move?

Well for this demonstration we are going to use a Wheel, it can be of any style, but one with spokes works best to demonstrate the Wagon Wheel effect.

Wheels, are circular 🙂 and circles have 360 degrees, if a wheel turns a full 360 degrees between each frame, then it will appear to stand still.

Some more Maths! Depending upon the number of Spokes in your wheel you can get different effects.

Lets start with one Spoke!

And to make things interesting we will create avariable so we can turn it by different degrees quite easily.

So we set it up to recieve the broadcast from the Movie Machine and turn round by a certain amount each time.

In the example above I have used the variable, but you don’t have to you can just put in a number.

Try the following numbers and see what effect you get:

90 – what do you see?

180 – what do you see?

360 – what do you see?

And if you want to get real fancy and use a variable, you can add the variable, and the following code to adjust whilst the program is running.

What next?

Try numbers very close to the ones above…

Try a wheel with different numbers of spokes and different numbers…

Remember the games we did last year? You could add a spinning ball…