INQ241B - Day 6 Notes

New section on creating games
First need to change the coding level on main screen choose ‘Skill level’ box and select ‘coder’
New script, instead of ‘blank turtle’ use ‘blank’
Add game library (add new, library, seach for game, click it)
Game library give us a bunch of functions (similar to how turtle library gave us a bunch of functions)
Need to start the game
```
var board := ♻game→start
```
Can set background image by using the board’s set background picture function
```
board→set background picture(✿Beautiful Background)
```
AppInventor has bunches of images in its data base you can search for them by searching for art and then search for a thing

Add a sprite with the create picture function

board→create picture(✿ Picture of Something)

It may be too big or too small
To change the attributes of a sprite, need to have a reference to it it
Can create a reference to it by storing it in a variable
Fortunately there is a ‘store in var’ button to make this easy
```
var sprite := board→create picture(✿ Picture of Something)
```
Note though that it gives you a name, if you want a different name there is a rename button.
Calling sprite functions is a lot like calling turtle functions
Find a list of all of them in the same way
Now we have access to sprite functions, like set width and set height
```
var sprite→set width(100)
```
Only need to set one the other will be set to maintain aspect ratio
Can also set the x y of the sprite
```
var sprite→set x(0)
```
Note the coordinate system

Can also set the x and y velocity of the sprite
```
var sprite→set speed x(100)
```
Try setting one
Try changing the sign
Try setting both
Try chaning the magnitude
But the sprite just goes off the screen
We can prevent it the same way we did with turtle

So we put

if sprite→x > board→width then
  sprite→set speed x(0)
else do nothing end if

But this doesn’t work, because all of the code in the main function is executed once before the animation starts

What we need is a way to run code at every frame of animation

board→on every frame do
  this code is executed every frame of animation
end

Calculate the new speed from the old speed

var new speed x := sprite→speed x * -1
sprite→set speed x(new speed)