8 files changed, 0 insertions, 657 deletions
diff --git a/six/resources/body.gif b/six/resources/body.gif
deleted file mode 100644
index 94a0956..0000000
--- a/six/resources/body.gif
+++ /dev/null
diff --git a/six/resources/goo-red.gif b/six/resources/goo-red.gif
deleted file mode 100644
index bf767b1..0000000
--- a/six/resources/goo-red.gif
+++ /dev/null
diff --git a/six/resources/goo.gif b/six/resources/goo.gif
deleted file mode 100644
index cb0d98b..0000000
--- a/six/resources/goo.gif
+++ /dev/null
diff --git a/six/resources/head.gif b/six/resources/head.gif
deleted file mode 100644
index 664f679..0000000
--- a/six/resources/head.gif
+++ /dev/null
diff --git a/six/resources/obstacle.gif b/six/resources/obstacle.gif
deleted file mode 100644
index 6ff288e..0000000
--- a/six/resources/obstacle.gif
+++ /dev/null
diff --git a/six/resources/tail.gif b/six/resources/tail.gif
deleted file mode 100644
index 6fbd317..0000000
--- a/six/resources/tail.gif
+++ /dev/null
diff --git a/six/snake.rkt b/six/snake.rkt
deleted file mode 100644
index c57b01c..0000000
--- a/six/snake.rkt
+++ /dev/null
@@ -1,295 +0,0 @@
-#lang racket
-(require 2htdp/universe 2htdp/image)
-
-;; data
-(struct pit (snake goos obstacles dinged))
-(struct snake (dir segs))
-(struct goo (loc expire type))
-(struct obstacle (loc expire))
-(struct posn (x y))
-
-;; constants
-(define TICK-RATE 1/10)
-
-(define SIZE 30)
-
-(define SEG-SIZE 15)
-
-(define EXPIRATION-TIME 150)
-(define OBSTACLE-EXPIRATION-TIME 250)
-
-(define WIDTH-PX (* SEG-SIZE 30))
-(define HEIGHT-PX (* SEG-SIZE 30))
-
-(define MT-SCENE (empty-scene WIDTH-PX HEIGHT-PX))
-(define GOO-IMG (bitmap "resources/goo.gif"))
-(define GOO-RED-IMG (bitmap "resources/goo-red.gif"))
-(define OBSTACLE-IMG (bitmap "resources/obstacle.gif"))
-(define SEG-IMG (bitmap "resources/body.gif"))
-(define HEAD-IMG (bitmap "resources/head.gif"))
-
-(define HEAD-LEFT-IMG HEAD-IMG)
-(define HEAD-DOWN-IMG (rotate 90 HEAD-LEFT-IMG))
-(define HEAD-RIGHT-IMG (flip-horizontal HEAD-LEFT-IMG))
-(define HEAD-UP-IMG (flip-vertical HEAD-DOWN-IMG))
-
-(define ENDGAME-TEXT-SIZE 15)
-
-;; main
-(define (start-snake)
-  (big-bang (pit (snake "right" (list (posn 1 1)))
-                 (list (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo))
-                 (list (fresh-obstacle)
-                       (fresh-obstacle))
-                 0)
-            (on-tick next-pit TICK-RATE)
-            (on-key direct-snake)
-            (to-draw render-pit)
-            (stop-when dead? render-end)))
-
-(define (next-pit w)
-  (define snake (pit-snake w))
-  (define goos (pit-goos w))
-  (define obstacles (pit-obstacles w))
-  (define dinged (pit-dinged w))
-  (define goo-to-eat (can-eat snake goos))
-  (if goo-to-eat
-      (pit (grow-size snake (goo-type goo-to-eat))
-           (age-goo (eat goos goo-to-eat))
-           (age-obstacle obstacles) (+ 1 dinged))
-      (pit (slither snake)
-           (age-goo goos)
-           (age-obstacle obstacles) dinged)))
-
-(define (direct-snake w ke)
-  (cond [(dir? ke) (world-change-dir w ke)]
-        [else w]))
-
-(define (render-pit w)
-  (snake+scene (pit-snake w)
-               (goo-list+scene (pit-goos w)
-                               (obstacle-list+scene
-                                (pit-obstacles w) MT-SCENE))))
-
-(define (dead? w)
-  (define snake (pit-snake w))
-  (or (self-colliding? snake)
-      (wall-colliding? snake)
-      (obstacle-colliding? snake (pit-obstacles w))))
-
-(define (render-end w)
-  (overlay (above (text "Game Over" ENDGAME-TEXT-SIZE "black")
-                  (text (string-append "You dinged "
-                                       (number->string (pit-dinged w))
-                                       " goos.")
-                        ENDGAME-TEXT-SIZE "black"))
-           (render-pit w)))
-
-
-;; clock
-(define (can-eat snake goos)
-  (cond [(empty? goos) #f]
-        [else (if (close? (snake-head snake) (first goos))
-                  (first goos)
-                  (can-eat snake (rest goos)))]))
-
-(define (eat goos goo-to-eat)
-  (append (list (fresh-goo)) (remove goo-to-eat goos)))
-
-(define (close? s g)
-  (posn=? s (goo-loc g)))
-
-(define (grow-size sn size)
-  (cond [(= size 0) sn]
-        [else (grow-size (grow sn) (- size 1))]))
-
-(define (grow sn)
-  (snake (snake-dir sn)
-         (cons (next-head sn) (snake-segs sn))))
-
-(define (slither sn)
-  (snake (snake-dir sn)
-         (cons (next-head sn) (all-but-last (snake-segs sn)))))
-
-(define (next-head sn)
-  (define head (snake-head sn))
-  (define dir (snake-dir sn))
-  (cond [(string=? dir "up") (posn-move head 0 -1)]
-        [(string=? dir "down") (posn-move head 0 1)]
-        [(string=? dir "left") (posn-move head -1 0)]
-        [(string=? dir "right") (posn-move head 1 0)]))
-
-(define (posn-move p dx dy)
-  (posn (+ (posn-x p) dx)
-        (+ (posn-y p) dy)))
-
-(define (all-but-last segs)
-  (cond [(empty? (rest segs)) empty]
-        [else (cons (first segs) (all-but-last (rest segs)))]))
-
-(define (age-goo goos)
-  (rot (renew goos)))
-
-(define (renew goos)
-  (cond [(empty? goos) empty]
-        [(rotten? (first goos))
-         (append (fresh-goos) (renew (rest goos)))]
-        [else
-         (append (list (first goos)) (renew (rest goos)))]))
-
-(define (rot goos)
-  (cond [(empty? goos) empty]
-        [else (cons (decay (first goos)) (rot (rest goos)))]))
-
-(define (rotten? g)
-  (zero? (goo-expire g)))
-
-(define (decay g)
-  (goo (goo-loc g) (sub1 (goo-expire g)) (goo-type g)))
-
-(define (fresh-goo)
-  (goo (posn (add1 (random (sub1 SIZE)))
-             (add1 (random (sub1 SIZE))))
-       EXPIRATION-TIME
-       (random 1 3)))
-
-(define (fresh-goos)
-  (define (gen-goos n)
-    (cond [(= n 0) empty]
-          [else (cons (fresh-goo) (gen-goos (- n 1)))]))
-  (let ((n (random 3)))
-    (gen-goos n)))
-
-(define (age-obstacle obstacles)
-  (rot-obstacles (renew-obstacles obstacles)))
-
-(define (renew-obstacles obstacles)
-  (cond [(empty? obstacles)  empty]
-        [(obstacle-expired? (first obstacles))
-         (cons (fresh-obstacle) (renew-obstacles (rest obstacles)))]
-        [else
-         (cons (first obstacles) (renew-obstacles (rest obstacles)))]))
-
-(define (rot-obstacles obstacles)
-  (cond [(empty? obstacles) empty]
-        [else (cons (decay-obstacle (first obstacles))
-                    (rot-obstacles (rest obstacles)))]))
-
-(define (obstacle-expired? obs)
-  (zero? (obstacle-expire obs)))
-
-(define (decay-obstacle obs)
-  (obstacle (obstacle-loc obs) (sub1 (obstacle-expire obs))))
-
-(define (fresh-obstacle)
-  (obstacle (posn (add1 (random (sub1 SIZE)))
-                  (add1 (random (sub1 SIZE))))
-            OBSTACLE-EXPIRATION-TIME))
-
-;; keys
-(define (dir? x)
-  (or (key=? x "up")
-      (key=? x "down")
-      (key=? x "left")
-      (key=? x "right")))
-
-(define (world-change-dir w d)
-  (define the-snake (pit-snake w))
-  (cond [(and (opposite-dir? (snake-dir the-snake) d)
-              (cons? (rest (snake-segs the-snake))))
-         (stop-with w)]
-        [else
-         (pit (snake-change-dir the-snake d)
-              (pit-goos w)
-              (pit-obstacles w)
-              (pit-dinged w))]))
-
-(define (opposite-dir? d1 d2)
-  (cond [(string=? d1 "up") (string=? d2 "down")]
-        [(string=? d1 "down") (string=? d2 "up")]
-        [(string=? d1 "left") (string=? d2 "right")]
-        [(string=? d1 "right") (string=? d2 "left")]))
-
-
-;; render
-(define (snake+scene snake scene)
-  (define snake-body-scene
-    (img-list+scene (snake-body snake) SEG-IMG scene))
-  (define dir (snake-dir snake))
-  (img+scene (snake-head snake)
-             (cond [(string=? "up" dir) HEAD-UP-IMG]
-                   [(string=? "down" dir) HEAD-DOWN-IMG]
-                   [(string=? "left" dir) HEAD-LEFT-IMG]
-                   [(string=? "right" dir) HEAD-RIGHT-IMG])
-             snake-body-scene))
-
-(define (goo-list+scene goos scene)
-  (define (get-posns-from-goo goos type)
-    (cond [(empty? goos) empty]
-          [(= (goo-type (first goos)) type)
-           (cons (goo-loc (first goos))
-                 (get-posns-from-goo (rest goos) type))]
-          [else (get-posns-from-goo (rest goos) type)]))
-  (img-list+scene (get-posns-from-goo goos 1) GOO-IMG
-                  (img-list+scene (get-posns-from-goo goos 2)
-                                  GOO-RED-IMG scene)))
-
-(define (obstacle-list+scene obstacles scene)
-  (define (get-posns-from-obstacle obstacles)
-    (cond [(empty? obstacles) empty]
-          [else (cons (obstacle-loc (first obstacles))
-                      (get-posns-from-obstacle (rest obstacles)))]))
-  (img-list+scene (get-posns-from-obstacle obstacles)
-                  OBSTACLE-IMG scene))
-
-(define (img-list+scene posns img scene)
-  (cond [(empty? posns) scene]
-        [else (img+scene
-               (first posns)
-               img
-               (img-list+scene (rest posns) img scene))]))
-
-(define (img+scene posn img scene)
-  (place-image img
-               (* (posn-x posn) SEG-SIZE)
-               (* (posn-y posn) SEG-SIZE)
-               scene))
-
-
-;; end game
-(define (self-colliding? snake)
-  (cons? (member (snake-head snake) (snake-body snake))))
-
-(define (wall-colliding? snake)
-  (define x (posn-x (snake-head snake)))
-  (define y (posn-y (snake-head snake)))
-  (or (= 0 x) (= x SIZE)
-      (= 0 y) (= y SIZE)))
-
-(define (obstacle-colliding? snake obstacles)
-  (cond [(empty? obstacles) #f]
-        [(posn=? (snake-head snake)
-                 (obstacle-loc (first obstacles))) #t]
-        [else (obstacle-colliding? snake (rest obstacles))]))
-
-;; aux
-(define (posn=? p1 p2)
-  (and (= (posn-x p1) (posn-x p2))
-       (= (posn-y p1) (posn-y p2))))
-
-(define (snake-head sn)
-  (first (snake-segs sn)))
-
-(define (snake-body sn)
-  (rest (snake-segs sn)))
-
-(define (snake-tail sn)
-  (last (snake-segs sn)))
-
-(define (snake-change-dir sn d)
-  (snake d (snake-segs sn)))
diff --git a/six/snakes.rkt b/six/snakes.rkt
deleted file mode 100644
index dae3468..0000000
--- a/six/snakes.rkt
+++ /dev/null
@@ -1,362 +0,0 @@
-#lang racket
-(require 2htdp/universe 2htdp/image)
-
-;; data
-(struct pit (snake-1 snake-2 goos obstacles dinged))
-(struct snake (dir segs))
-(struct goo (loc expire type))
-(struct obstacle (loc expire))
-(struct posn (x y))
-
-;; constants
-(define TICK-RATE 1/10)
-
-(define SIZE 30)
-
-(define SEG-SIZE 15)
-
-(define EXPIRATION-TIME 150)
-(define OBSTACLE-EXPIRATION-TIME 250)
-
-(define WIDTH-PX (* SEG-SIZE 30))
-(define HEIGHT-PX (* SEG-SIZE 30))
-
-(define MT-SCENE (empty-scene WIDTH-PX HEIGHT-PX))
-(define GOO-IMG (bitmap "resources/goo.gif"))
-(define GOO-RED-IMG (bitmap "resources/goo-red.gif"))
-(define OBSTACLE-IMG (bitmap "resources/obstacle.gif"))
-(define SEG-IMG (bitmap "resources/body.gif"))
-(define HEAD-IMG (bitmap "resources/head.gif"))
-
-(define HEAD-LEFT-IMG HEAD-IMG)
-(define HEAD-DOWN-IMG (rotate 90 HEAD-LEFT-IMG))
-(define HEAD-RIGHT-IMG (flip-horizontal HEAD-LEFT-IMG))
-(define HEAD-UP-IMG (flip-vertical HEAD-DOWN-IMG))
-
-(define ENDGAME-TEXT-SIZE 15)
-
-;; main
-(define (start-snakes)
-  (big-bang (pit (snake "right" (list (posn 1 1)))
-                 (snake "d" (list (posn 1 10)))
-                 (list (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo)
-                       (fresh-goo))
-                 (list (fresh-obstacle)
-                       (fresh-obstacle))
-                 0)
-            (on-tick next-pit TICK-RATE)
-            (on-pad direct-snakes)
-            (to-draw render-pit)
-            (stop-when dead? render-end)))
-
-(define (next-pit w)
-  (define snake-1 (pit-snake-1 w))
-  (define snake-2 (pit-snake-2 w))
-  (define goos (pit-goos w))
-  (define obstacles (pit-obstacles w))
-  (define dinged (pit-dinged w))
-  (define goo-to-eat-sn1 (can-eat snake-1 goos))
-  (define goo-to-eat-sn2 (can-eat snake-2 goos))
-  (cond [(and goo-to-eat-sn1 goo-to-eat-sn2) ; sn1 and sn2 dinged.
-         (pit (grow-size snake-1 (goo-type goo-to-eat-sn1))
-              (grow-size snake-2 (goo-type goo-to-eat-sn2))
-              (age-goo (eat (eat goos goo-to-eat-sn1) goo-to-eat-sn2))
-              (age-obstacle obstacles) (+ 2 dinged))]
-        [(and goo-to-eat-sn1 (not goo-to-eat-sn2)) ; sn1 dinged.
-         (pit (grow-size snake-1 (goo-type goo-to-eat-sn1))
-              (slither  snake-2)
-              (age-goo (eat goos goo-to-eat-sn1))
-              (age-obstacle obstacles) (+ 1 dinged))]
-        [(and (not goo-to-eat-sn1) goo-to-eat-sn2) ; sn2 dinged.
-         (pit (slither  snake-1)
-              (grow-size snake-2 (goo-type goo-to-eat-sn2))
-              (age-goo (eat goos goo-to-eat-sn2))
-              (age-obstacle obstacles) (+ 1 dinged))]
-        [else ; none dinged.
-         (pit (slither snake-1)
-              (slither snake-2)
-              (age-goo goos)
-              (age-obstacle obstacles) dinged)]))
-
-
-(define (direct-snakes w ke)
-  (cond [(arrow-key? ke) (direct-snake-1 w ke)]
-        [(wasd-key? ke) (direct-snake-2 w ke)]
-        [else w]))
-
-(define (direct-snake-1 w ke)
-  (world-change-dir 1 w ke))
-
-(define (direct-snake-2 w ke)
-  (world-change-dir 2 w ke))
-
-(define (render-pit w)
-  (snake+scene (pit-snake-1 w)
-               (snake+scene (pit-snake-2 w)
-                            (goo-list+scene (pit-goos w)
-                                            (obstacle-list+scene
-                                             (pit-obstacles w) MT-SCENE)))))
-
-(define (dead? w)
-  (define snake-1 (pit-snake-1 w))
-  (define snake-2 (pit-snake-2 w))
-  (define (colliding? sn sn-other)
-    (or (self-colliding? sn)
-        (wall-colliding? sn)
-        (obstacle-colliding? sn (pit-obstacles w))
-        (snake-colliding? sn sn-other)))
-  (or (colliding? snake-1 snake-2) (colliding? snake-2 snake-1)))
-
-(define (render-end w)
-  (overlay (above (text "Game Over" ENDGAME-TEXT-SIZE "black")
-                  (text (string-append "Dinged "
-                                       (number->string (pit-dinged w))
-                                       " goos.")
-                        ENDGAME-TEXT-SIZE "black"))
-           (render-pit w)))
-
-
-;; clock
-(define (can-eat snake goos)
-  (cond [(empty? goos) #f]
-        [else (if (close? (snake-head snake) (first goos))
-                  (first goos)
-                  (can-eat snake (rest goos)))]))
-
-(define (eat goos goo-to-eat)
-  (append (list (fresh-goo)) (remove goo-to-eat goos)))
-
-(define (close? s g)
-  (posn=? s (goo-loc g)))
-
-(define (grow-size sn size)
-  (cond [(= size 0) sn]
-        [else (grow-size (grow sn) (- size 1))]))
-
-(define (grow sn)
-  (snake (snake-dir sn)
-         (cons (next-head sn) (snake-segs sn))))
-
-(define (slither sn)
-  (snake (snake-dir sn)
-         (cons (next-head sn) (all-but-last (snake-segs sn)))))
-
-(define (next-head sn)
-  (define head (snake-head sn))
-  (define dir (snake-dir sn))
-  (cond [(or (string=? dir "up") (string=? dir "w")) (posn-move head 0 -1)]
-        [(or (string=? dir "down") (string=? dir "s")) (posn-move head 0 1)]
-        [(or (string=? dir "left") (string=? dir "a")) (posn-move head -1 0)]
-        [(or (string=? dir "right") (string=? dir "d")) (posn-move head 1 0)]))
-
-(define (posn-move p dx dy)
-  (posn (+ (posn-x p) dx)
-        (+ (posn-y p) dy)))
-
-(define (all-but-last segs)
-  (cond [(empty? (rest segs)) empty]
-        [else (cons (first segs) (all-but-last (rest segs)))]))
-
-(define (age-goo goos)
-  (rot (renew goos)))
-
-(define (renew goos)
-  (cond [(empty? goos) empty]
-        [(rotten? (first goos))
-         (append (fresh-goos) (renew (rest goos)))]
-        [else
-         (append (list (first goos)) (renew (rest goos)))]))
-
-(define (rot goos)
-  (cond [(empty? goos) empty]
-        [else (cons (decay (first goos)) (rot (rest goos)))]))
-
-(define (rotten? g)
-  (zero? (goo-expire g)))
-
-(define (decay g)
-  (goo (goo-loc g) (sub1 (goo-expire g)) (goo-type g)))
-
-(define (fresh-goo)
-  (goo (posn (add1 (random (sub1 SIZE)))
-             (add1 (random (sub1 SIZE))))
-       EXPIRATION-TIME
-       (random 1 3)))
-
-(define (fresh-goos)
-  (define (gen-goos n)
-    (cond [(= n 0) empty]
-          [else (cons (fresh-goo) (gen-goos (- n 1)))]))
-  (let ((n (random 3)))
-    (gen-goos n)))
-
-(define (age-obstacle obstacles)
-  (rot-obstacles (renew-obstacles obstacles)))
-
-(define (renew-obstacles obstacles)
-  (cond [(empty? obstacles)  empty]
-        [(obstacle-expired? (first obstacles))
-         (cons (fresh-obstacle) (renew-obstacles (rest obstacles)))]
-        [else
-         (cons (first obstacles) (renew-obstacles (rest obstacles)))]))
-
-(define (rot-obstacles obstacles)
-  (cond [(empty? obstacles) empty]
-        [else (cons (decay-obstacle (first obstacles))
-                    (rot-obstacles (rest obstacles)))]))
-
-(define (obstacle-expired? obs)
-  (zero? (obstacle-expire obs)))
-
-(define (decay-obstacle obs)
-  (obstacle (obstacle-loc obs) (sub1 (obstacle-expire obs))))
-
-(define (fresh-obstacle)
-  (obstacle (posn (add1 (random (sub1 SIZE)))
-                  (add1 (random (sub1 SIZE))))
-            OBSTACLE-EXPIRATION-TIME))
-
-;; keys
-(define (dir? x)
-  (or (arrow-key? x)
-      (wasd-key? x)))
-
-(define (arrow-key? x)
-  (or (key=? x "up")
-      (key=? x "down")
-      (key=? x "left")
-      (key=? x "right")))
-
-(define (wasd-key? x)
-  (or (key=? x "w")
-      (key=? x "s")
-      (key=? x "a")
-      (key=? x "d")))
-
-(define (world-change-dir sn-number w d)
-  (define snake-1 (pit-snake-1 w))
-  (define snake-2 (pit-snake-2 w))
-  (cond [(and (= sn-number 1) ;snake-1
-              (opposite-dir? (snake-dir snake-1) d)
-              (cons? (rest (snake-segs snake-1))))
-         (stop-with w)]
-        [(and (= sn-number 2) ;snake-2
-              (opposite-dir? (snake-dir snake-2) d)
-              (cons? (rest (snake-segs snake-2))))
-         (stop-with w)]
-        [(= sn-number 1) ;snake-1 change dir.
-         (pit (snake-change-dir snake-1 d)
-              (pit-snake-2 w)
-              (pit-goos w)
-              (pit-obstacles w)
-              (pit-dinged w))]
-        [else ;snake-2 change dir.
-         (pit (pit-snake-1 w)
-              (snake-change-dir snake-2 d)
-              (pit-goos w)
-              (pit-obstacles w)
-              (pit-dinged w))]))
-
-(define (opposite-dir? d1 d2)
-  (cond [(string=? d1 "up") (string=? d2 "down")]
-        [(string=? d1 "down") (string=? d2 "up")]
-        [(string=? d1 "left") (string=? d2 "right")]
-        [(string=? d1 "right") (string=? d2 "left")]
-        [(string=? d1 "w") (string=? d2 "s")]
-        [(string=? d1 "s") (string=? d2 "w")]
-        [(string=? d1 "a") (string=? d2 "d")]
-        [(string=? d1 "d") (string=? d2 "a")]))
-
-
-;; render
-(define (snake+scene snake scene)
-  (define snake-body-scene
-    (img-list+scene (snake-body snake) SEG-IMG scene))
-  (define dir (snake-dir snake))
-  (img+scene (snake-head snake)
-             (cond [(or (string=? "up" dir) (string=? "w" dir))
-                    HEAD-UP-IMG]
-                   [(or (string=? "down" dir) (string=? "s" dir))
-                    HEAD-DOWN-IMG]
-                   [(or (string=? "left" dir) (string=? "a" dir))
-                    HEAD-LEFT-IMG]
-                   [(or (string=? "right" dir) (string=? "d" dir))
-                    HEAD-RIGHT-IMG])
-             snake-body-scene))
-
-(define (goo-list+scene goos scene)
-  (define (get-posns-from-goo goos type)
-    (cond [(empty? goos) empty]
-          [(= (goo-type (first goos)) type)
-           (cons (goo-loc (first goos))
-                 (get-posns-from-goo (rest goos) type))]
-          [else (get-posns-from-goo (rest goos) type)]))
-  (img-list+scene (get-posns-from-goo goos 1) GOO-IMG
-                  (img-list+scene (get-posns-from-goo goos 2)
-                                  GOO-RED-IMG scene)))
-
-(define (obstacle-list+scene obstacles scene)
-  (define (get-posns-from-obstacle obstacles)
-    (cond [(empty? obstacles) empty]
-          [else (cons (obstacle-loc (first obstacles))
-                      (get-posns-from-obstacle (rest obstacles)))]))
-  (img-list+scene (get-posns-from-obstacle obstacles)
-                  OBSTACLE-IMG scene))
-
-(define (img-list+scene posns img scene)
-  (cond [(empty? posns) scene]
-        [else (img+scene
-               (first posns)
-               img
-               (img-list+scene (rest posns) img scene))]))
-
-(define (img+scene posn img scene)
-  (place-image img
-               (* (posn-x posn) SEG-SIZE)
-               (* (posn-y posn) SEG-SIZE)
-               scene))
-
-
-;; end game
-(define (self-colliding? snake)
-  (cons? (member (snake-head snake) (snake-body snake))))
-
-(define (wall-colliding? snake)
-  (define x (posn-x (snake-head snake)))
-  (define y (posn-y (snake-head snake)))
-  (or (= 0 x) (= x SIZE)
-      (= 0 y) (= y SIZE)))
-
-(define (obstacle-colliding? snake obstacles)
-  (cond [(empty? obstacles) #f]
-        [(posn=? (snake-head snake)
-                 (obstacle-loc (first obstacles))) #t]
-        [else (obstacle-colliding? snake (rest obstacles))]))
-
-(define (snake-colliding? snake snake-other)
-  (define (head-in-other sn other)
-    (cond [(empty? other) #f]
-          [(posn=? sn (first other)) #t]
-          [else (head-in-other sn (rest other))]))
-  (head-in-other (snake-head snake) (snake-segs snake-other)))
-
-;; aux
-(define (posn=? p1 p2)
-  (and (= (posn-x p1) (posn-x p2))
-       (= (posn-y p1) (posn-y p2))))
-
-(define (snake-head sn)
-  (first (snake-segs sn)))
-
-(define (snake-body sn)
-  (rest (snake-segs sn)))
-
-(define (snake-tail sn)
-  (last (snake-segs sn)))
-
-(define (snake-change-dir sn d)
-  (snake d (snake-segs sn)))