I am currently trying to code 'Breakout' in BSL but I'm stuck as I don't know how to add a welcome and a game-over screen to my code. It is supposed that the game starts with the welcome screen and when it is clicked with the mouse on the screen the actual game should start. When the ball collides with the lower edge of the screen a game-over-screen is supposed to appear. I appreciate any tips given!
(define WIDTH 200)
(define HEIGHT 200)
(define BALL-RADIUS 10)
(define BALL-IMG (circle BALL-RADIUS "solid" "red"))
(define MT (empty-scene WIDTH HEIGHT))
(define GAME-OVER
(place-image (text "Game-over" 30 "black")
100 100
MT))
(define WELCOME
(place-image (text "Welcome" 30 "black")
100 100
MT))
(define-struct vel (delta-x delta-y))
; a Vel is a structure: (make-vel Number Number)
; interp. the velocity vector of a moving object
(define-struct ball (loc velocity))
; a Ball is a structure: (make-ball Posn Vel)
; interp. the position and velocity of a object
(define RACKET (rectangle 30 10 "solid" "grey"))
(define-struct world-state (ball racket))
; A WorldState is a structure. (make-world-state Ball Location of
Racket)
; interp. current velocity and location of ball, current location of
racket
; Posn Vel -> Posn
; applies q to p and simulates the movement in one clock tick
(check-expect (posn+vel (make-posn 5 6) (make-vel 1 2))
(make-posn 6 8))
(define (posn+vel p q)
(make-posn (+ (posn-x p) (vel-delta-x q))
(+ (posn-y p) (vel-delta-y q))))
; Ball -> Ball
; computes movement of ball in one clock tick
(define (move-ball ball)
(make-ball (posn+vel (ball-loc ball)
(ball-velocity ball))
(ball-velocity ball)))
; A Collision is either
; - "top"
; - "down"
; - "left"
; - "right"
; - "racket"
; - "none"
; interp. the location where a ball collides with a wall
; Posn -> Collision
; detects with which of the walls (if any) or the racket the ball
collides
(define (collision world-state)
(cond
[(<= (posn-x (ball-loc (world-state-ball world-state))) BALL-
RADIUS) "left"]
[(<= (posn-y (ball-loc (world-state-ball world-state))) BALL-
RADIUS) "top"]
[(>= (posn-x (ball-loc (world-state-ball world-state))) (- WIDTH
BALL-RADIUS)) "right"]
[(>= (posn-y (ball-loc (world-state-ball world-state))) (- HEIGHT
BALL-RADIUS)) "down"]
[(and (>= (posn-y (ball-loc (world-state-ball world-state))) (-
HEIGHT BALL-RADIUS 10))
(<= (- (posn-x (world-state-racket world-state)) 15)
(posn-x (world-state-racket world-state))
(+ (posn-x (world-state-racket world-state)) 15)))
"racket"]
[else "none"]))
; Vel Collision -> Vel
; computes the velocity of an object after a collision
(define (bounce vel collision)
(cond [(or (string=? collision "left")
(string=? collision "right"))
(make-vel (- (vel-delta-x vel))
(vel-delta-y vel))]
[(or (string=? collision "top")
(string=? collision "racket"))
(make-vel (vel-delta-x vel)
(- (vel-delta-y vel)))]
[else vel]))
; render
; WorldState -> Image
; renders ball and
racket at their position
(check-expect (image? (render INITIAL-STATE)) #true)
(define (render world-state)
(place-image BALL-IMG
(posn-x (ball-loc (world-state-ball world-state)))
(posn-y (ball-loc (world-state-ball world-state)))
(place-image RACKET
(posn-x (world-state-racket world-state))
195
(empty-scene WIDTH HEIGHT))))
;tick
; WorldState -> WorldState
; moves ball to its next location
(check-expect (tick INITIAL-STATE) (make-world-state (make-ball (make-posn 21 14) (make-vel 1 2)) (make-posn 20 195)))
(define (tick world-state)
(make-world-state (move-ball (make-ball (ball-loc (world-state-ball world-state))
(bounce (ball-velocity (world-state-ball world-state))
(collision world-state))))
(world-state-racket world-state)))
; A Location is a structure: (make-posn Number Number)
; interp. x and y coordinate of a location on screen.
(define Loc (make-posn 1 1))
; A MouseEvent is one of
; - "button-down"
; - "button-up"
; - "drag"
; - "move"
; - "enter"
; - "leave"
; interp. mouse events, e.g., mouse movements or mouse clicks
(define MOUSE-CLICK "button-down")
; mouse
;
; Game Number Number MouseEvent -> WorldState
; Update position of racket when the mouse moves
;mouse-template
(define (mouse-template world-state mouse-loc-x mouse-loc-y MouseEvent)
(cond
((string=? MouseEvent "button-down")...)
((string=? MouseEvent "button-up")...)
((string=? MouseEvent "drag")...)
((string=? MouseEvent "move")...)
((string=? MouseEvent "enter")...)
((string=? MouseEvent "leave")...)
(else ...)))
(define (mouse world-state mouse-loc-x mouse-loc-y MouseEvent)
(cond
[(and (string=? MouseEvent "move")
(>= mouse-loc-y 180))
(make-world-state (world-state-ball world-state)
(make-posn mouse-loc-x 195))]
[else world-state]))
(define INITIAL-BALL (make-ball (make-posn 20 12)
(make-vel 1 2)))
(define INITIAL-RACKET (make-posn 20 195))
(define INITIAL-STATE (make-world-state INITIAL-BALL INITIAL-RACKET))
; WorldState -> WorldState
; Starts the game
(define (main state)
(big-bang state
(on-tick tick 0.01)
(to-draw render)
(on-mouse mouse)))
; start with INITIAL-STATE
You now have three different states:
So far you have only had "playing" and you used your world structure to represent that.
Now you need to introduce two new structures: welcome and game-over.
Rename your old render function render-world (or render-playing).
Then write something like:
(define (render w)
(cond
[(welcome? w) (render-welcome w)]
[(world? w) (render-world w)]
[(game-over? w) (render-game-over w)]))
Of course your initial state should become an instance of welcome, and you also need three different tick functions.