My name: Hung Q. Nguyen
Write what you did!
Initial thought: I wanted to make a circle that smoothly making a "Cardioid" animation. More infomation about Cardioid: https://en.wikipedia.org/wiki/Cardioid
Result: Not quite as I expected because the value of alpha is not corresponding to the value of height when height get decreased by time.
What I did: - Using 2htpd image to create a circle with 50px as a radius and filled with blue color.
```
(define ball
(circle 50 "solid" "blue"))
```
- I define a function called "initscreen" to initialize a screen (500x500) and animate the ball with the equation x and y provided to make the "Cardioid" animation which is provided in the wiki page.
```
(define (initscreen height)
(place-image ball
(+ 350 (* 2 (* 50 (* (cos height) (- 1 (cos height))))))
(+ 250 (* 2 (* 50 (* (sin height) (- 1 (cos height))))))
(empty-scene 500 500)))
```
-
I define a function bounding which will decrease 5px of the position of the height by each milisecond.
(define (bounding height) (- height 5)) -
Using the defined function big-bang in 2htpd universe to make run Cardioid animation for 5000/100 seconds (it will also stop when height reaches 0).
(big-bang 500 (on-tick bounding) (to-draw initscreen) (stop-when zero?))
