QUIZ!• You can bring notes you took during class

• Any concept/topic we’ve covered may be up for grabs

Review

LET’S REVIEW SOME THINGS• What do we call the elements that make up the ‘grid’ that is the area our program

is drawn in?

• What’s the size of the Stage?

• X: -240 to 240

• Y: -180 to 180

LET’S REVIEW SOME THINGS• What are the terms on the 3 tabs at the top of the main coding area?

• Scripts, Costumes, Sounds

• If I want to change the ‘look’ of a sprite what’s the easiest way?

• Change the costume

• What’s the easiest way to copy some code?

• Right-click and duplicate

• In what section is the ‘Wait’ command?

Control

• What color is the ‘Sound’ section?

WHAT IS COMPUTER SCIENCE?

• Computing is a Creative Activity

• Abstraction reduces information and detail to facilitate focus on relevant topic

• Rocket launch - calls around to 10 different systems. Launch coordinator doesn't need to know the details about all of the subsystems.

• Data and information facilitate the creation of knowledge

• Algorithms are used to develop and express solutions to computational problems

• Programming enables problem solving, human expression, and creation of knowledge

• The Internet pervades modern computing

• Computing has global Impacts

Here’s what I might have said…

• Computer programming is about giving instructions to a computer

• Telling a computer what to do

• Computer programming is the art of creating something a computer interprets

• Computer programming is the what and how of what a computer does

WHAT IS COMPUTER SCIENCE (CS) – PARTIAL ANSWER

Abstraction

ABSTRACTION• Such a weird word….

• Let’s see if we can figure it out

• What does abstract mean?

ABSTRACTION REVIEWED• Let’s try some examples…

• How does a car work?

• Can you drive a car?

• How does a computer work?

• Can you use a computer?

• How is chocolate made?

• Can you eat it and enjoy it?

• How are your clothes made?

• Can you wear them?

ABSTRACTION• So we can USE all those things, and yet we have no idea how they work

• In computer science, abstraction is the same thing

• The way in which code WORKS, doesn’t prevent you from using it…

ABSTRACTION• How does move work for example?

• Something must be turning the pixels on and off from one area, to the next

• Do you know how?

• That’s abstraction

• The WAY in which move works, doesn’t mean you can’t use it!

ABSTRACTION• So, abstraction means…

• The WAY something works, is separated from its ability to be used

• How a car works is abstracted from someone driving it

• In coding, all you see is move. Or repeat. Or change costume

• HOW each of those works is separate from them

ABSTRACTION• The best example of us doing this, is making a block

• We hide the implementation. All someone sees (unless they choose to look harder) is say, ‘Draw Platforms’

• If I read your code, that could tell me enough! I may be quite happy just seeing that

The implementation of the code is kept separate from the usable part

Golden Code

GOLDEN CODE: WHAT IS IT?• This is a term used in Computer Science… what does it mean?

• Golden code refers to code which is perfect or ideal

• This means you can take it as is and use in a project

GOLDEN CODE: WHAT IS IT?• The code the teachers give you is nearly golden

• We could coin a new phrase? Silver code

• What this means is for your projects, pay attention, follow along, and save the code

• You will be able to use much of what we do as a group directly in your project

NEW TOPIC! SENSING• We’ve done some of this already!

• If you made your Mario project have a goal, then the easiest way to detect the goal would be, if Mario touched the goal object

NEW TOPIC! SENSING• Sensing is about determining …

• When one object is touching something else (or how far away it is from something else)

Or

• A key is pressed

Or

• The mouse is clicked

Or

• Timing

Or

• Noise

Or

• The value of an attribute or object

NEW TOPIC! SENSING

• There’s 5 things that can be sensed

1. An object can sense if it is touching a color

• Really cool feature!

• But…

• Problematic!

• What if I make say a platform, but it’s multiple colors?

• What if the color I sense exists elsewhere in my program?

• Still useful, but caution urged

Touching

NEW TOPIC! SENSING

• There’s 5 things that can be sensed

2. Any object can sense if one color is touching another color

• Very similar to ‘touching color’, but it detects when 2 colors collide

• caution urged

Touching

NEW TOPIC! SENSING

• There’s 5 things that can be sensed

3. An object can sense if it is touching the edge

• Exceptionally limited

• Only one command supported: ‘bounce’

• Notice, this is in the motion section, because of the ‘bounce’

• But, a very cool, and useful way to say, let a ball bounce off the side of the screen (hint, hint)

Touching

NEW TOPIC! SENSING

• There’s 5 things that can be sensed

4. An object can sense if it is touching another object

• This is the coolest command

• Allows one object to sense when it is touching another

• Then, it can react

• If I’m touching <some object>

• I win

• I die

• I get 50 points

• Most robust sensing command

Touching

NEW TOPIC! SENSING• There’s 5 things that can be sensed

5. An object can sense if it is near another object

• Useful if you want a sprite to change its behavior with proximity

• Handy, because otherwise you’d have to figure this out yourself

Touching

NEW TOPIC! SENSING• Hmmmm….

• Can my app use all of these? Or 2 or 3 of them?

• Of course it can!

• Will this be useful in Pong?

• You bet it will!

• Are there any gotchas?

• always

NEW TOPIC! SENSING• Let’s make something that bounces a ball around the screen

NEW TOPIC! SENSING• Time to try it out yourself!

• Create a new project

• Change your sprites costume. Set its size

• Randomize your position, and direction

• Copy the sprite

• Change the costume of the second sprite

• When the first sprite touches the second make it ‘bounce’

• Make a background with a specific color somewhere on it (like a ‘sun’)

• If either of your sprites hits that color, make them ‘bounce’

• When either sprite hits anything else a total of <x> times (such as 5). Use a variable per sprite!

• stop everything, and show a ‘game over’ screen

NEW TOPIC! SENSING• Make a background with a specific color somewhere on it

• If either of your sprites hits that color, make them ‘bounce’

• When either sprite hits anything else a total of <x> times (such as 5)

• stop everything, and show a ‘game over’ screen

IF ON EDGE, BOUNCE

DIRECTION

VARIABLES

VARIABLES

• Used to store information

• Are by their nature temporary• This differentiates them from databases or data stores such as files

• Have values that can change• Hence their name!

• Differentiates them from ‘constants’, values that do NOT change (we won’t see those in Snap!)

VARIABLES• So, what things might change in the real world, that we want to measure? I’ll give some

examples….

• Number of cars in a parking lot

• Number of points by the Seahawks in a game

• And their opponents!

• Number of clean socks I have left

• The current time (do I have to get up yet?)

• Amount of money in my bank account

• Number of Olympians in the Olympics

VARIABLES• In pairs, YOU come up with some examples

• You have 4 minutes to come up with 5 examples in your pairs

VARIABLES• SO why STORE that information?

• It allows us to remember what a value WAS

• How do I track the number of cars in a parking lot, without counting?

• Well, when you count, you are effectively using a variable

• That way we can …

• Keep track of a value that’s changing

• Pass it around to other parts of the system

• And they can react to it if it changes!

• Show it to the user!

VARIABLES• There are some existing variables for standard apps we’ve built!

• x position

• This is the position of the sprite it refers to

• y position

• direction

• costume #

• size

• give me some others!!!

• What does a variable look like in BYOB?

VARIABLES• Game

• Ask the user 5 questions

• Then, ASK them what they answered to each of your questions

• If they type in the right answer say ‘correct’

• Otherwise, say ‘wrong!’