Scratch

What is one thing that you like? PHYSICS & COSMOLOGY ROCK!!!!

Because this is a new scratcher class, students will have a lot to learn. The best way to memorize all the blocks and panes is to lean it yourself. I'll help you if you are stuck, but its best to try yourself first.

Lesson 1: Introducing the Interface
What you will learn: -the three main parts of the program
-how to use blocks to create scripts

Lets get used to the program first.
On the screen there are three main parts: the screen/stage (top right), sprites (bottom right), and scripts (left). The stage is where your projects function. The sprites are your characters, and your scripts are your commands.
Commands are built with blocks, each of which have a specific function. They are separated into 8 categories.

Let's try something simple first. When you open the program, you get a default cat sprite. Lets make him do something. Go to the controls blocks and drag out the "when green flag clicked" block. It looks like:

when gf clicked

Drag it out to the cat's scripts area, with the grey striped background.

What this block does is run everything below it when the green flag is clicked. The green flag is just the play/restart button for a project. You can find it in the top right corner of the screen/stage, next to a stop sign.

If you press the green flag, you'll notice that nothing happens. That's because all you've told the cat is:
"When I tell you go to,"
and you haven't told it to do anything besides wait for the start.

Lets go to the "Looks" category and drag out next costume:

next costume

which tells the cat "switch to your next costume".

If you notice, sprites can have different costumes, or way they look. On top of the scripts pane, there are three tabs: Scripts, Costumes, and Sounds. They store all the media and data for each sprite.

By default, the cat has two costumes, so we don't have to worry about adding one for now.

If you drag the next costume block right below the "when green flag clicked" block, you'll notice that it snaps together. This means they are connected. Now the command you've given to the cat is:
"When I tell you to start, switch to your next costume."

Try pressing the green flag!

You'll notice that the Scratch Cat changes picture! Try pressing it again! And again! And again! And--never mind. You get the idea.

[Sidenote: Why does the costume go back and forth?
When a sprite is told to go to the next costume when it's at the last costume, it doesn't have a "next costume" to go to. Therefore, it changes to the first costume. So your cat is going: costume 1--costume 2--costume 1--costume 2... If there were three costumes, you would have 1-2-3-1-2-3-1-2-3...]

Congratulations, you've created your first project! It may seem simple, but it still is a project. When we keep adding on more and more blocks, we can get full games! Try the following assignment to make sure you've learned what you need to know. Make sure to tell me if you're having trouble with part of any lesson.

Assignment 1: User Interaction!
Currently, we can only make the cat do something every time the project starts. What if we want the cat to change on space? Let's see.
A hat block, or block with a curve on top, is one that starts things and detects for things to happen, causing the rest of the script to start.

Let's get this block:

when key [space v] pressed

Let's attach a move 10 steps and if on edge, bounce block to it both from motion.

You should get this:

when key [space v] pressed
move (10) steps
if on edge, bounce

Now, try pressing the green flag. You'll still have the change in costume from our older script, but nothing else will happen. Now, try pressing space! If you did it correctly, the cat will move forward!

Now... You're probably wondering what the "if on edge, bounce" block is for. Try pressing space until the cat reaches the end of the screen. Keep pressing... and oh! The cat turns around! Therefore we can conclude that the "if on edge, bounce" block turns around when touching an edge.

You've just made an even more complicated project! You can even change the (10) from the "move 10 steps" to make it move farther or shorter. Try it!

Now, your assignment: I'd like to you to experiment a bit. Try new blocks, and see how they turn out. If you don't know how to use a block, don't worry, you can ask me or wait for me to cover it in our next lessons. Here's the requirement for the assignment:
-upload a project with those two scripts we covered to make sure you've assembled them correctly
-add some more blocks that you've figured out how to use
-add the

turn cw (15) degrees

to a

when key [space v] pressed

block (or the counterclockwise arrow works too). Can you figure out how it works? A tip: click on the [space v] on the block and change the key to be pressed!

When you've done all that, tell me here with a link to the project. If you can't figure out how to link a project, I can teach you. But tell me that you're done first. (just copy and paste the url from the top of your browser)

Good luck with your project!

PS. Feel free to add costumes to the cat. If you can't figure out how to do that, don't worry. I'll teach you next lesson.

Last edited by kayybee (2012-10-22 19:36:54)

ahirbhairav wrote:

Is it OK if I upload it on my alt account? the username is charukeshi.

Sure. Just make sure you link to it so I'll know its yours.

Thanks! I'll add pictures later. I was kinda busy.