Another try with HTDP 2nd Edition
(define BOARDWIDTH 200) (define BOARDHEIGHT 200) (define STARTPOSITION 50) (define BOARDBKGR "blue") (define GAMEBOARD (empty-scene BOARDWIDTH BOARDHEIGHT BOARDBKGR)) (define ROCKET .) (define UFO (overlay (circle 10 "solid" "red") (rectangle 40 4 "solid" "green"))) (define FLATBED (rectangle 60 10 "outline" "black")) (define (SPACESHIP option) (cond [(= option 1) ROCKET] [(= option 2) UFO])) (define SHOWNSHIP (SPACESHIP 1)) (define V 10) ;Velocity (define A 1) ;Acceleration (define (distance t) ;t = Time (- (* V t) (* 1/2 A (sqr t)))) (define SPACESHIP-BOTTOM (- BOARDHEIGHT (/ (image-height SHOWNSHIP) 2))) (define (render-shownship x y) (place-image SHOWNSHIP x y GAMEBOARD)) (define (create-rocket-scene.v7 t) (cond [(<= (distance t) SPACESHIP-BOTTOM) (render-shownship STARTPOSITION (distance t))] [(> (distance t) SPACESHIP-BOTTOM) (render-shownship STARTPOSITION SPACESHIP-BOTTOM)]))
This code is based off of Chapter 1 of HTDP. I've gotten this far and it wasn't as bad as last time. And it's been 5 years (I can't believe it) since I've touched this language. The only issues I have really are two things.
- I couldn't find a way to do one of the suggestions. Which was: How would change the program so that the rocket lands on a flat rock bed that is 10 pixels higher than the bottom of the scene? Don’t forget to change the scenery, too. When I tried adding another function call to render-shownship, I kept getting an error.
- The spaceship goes down to the bottom of the screen, then accelerates up the screen. I'm a bit lost on why that is.
Outside of those two things. I'm quite happy with my progress. I've thankfully gotten over the prefix issue as well, lol.