A game of snake.cljs

;; # A game of snake

;; First create the board that the snake will move on. For now the board is just an empty rectangle, but it's a cell so what's inside it can change. We'll update the board later so it contains the snake.

(defcell board 
  (let [square #(colorize "white" (rectangle 10 10))]
    (->> (range 20))
    (apply above (map #(apply beside (map square (range 20))) (range 20)))))

(defcell last-key nil)

(defcell direction [self]
  (or
    (get {37 :left
  	      38 :up
          39 :right
          40 :down} @last-key)
    @self
    :down))

(defcell snake [[2 2] [2 3] [2 4] [2 5]])

(defn move-piece [[x y]]
  (let [[x+ y+] (case @direction 
                  :left [dec identity] 
                  :right [inc identity] 
                  :up [identity dec] 
                  :down [identity inc])
        wrap #(cond (< % 0) 9 (> % 9) 0 :else %)]
    [(wrap (x+ x)) (wrap (y+ y))]))

(defn move! []
  (swap! snake #(conj (butlast %) (move-piece (first %)))))

(defn compute-board []
  (->>
    (for [y (range 10)
          x (range 10)]
      (cond->> (colorize "white" (rectangle 20 20)) (some #{[x y]} @snake) (colorize "blue")))
    (partition 10)
    (map #(apply beside %))
    (apply above)))

(defn tick! []
  (move!)
  (reset! board (compute-board))
  nil)

(defcell game-loop []
  (interval 200 tick!))

(goog.events.listen js/document  goog.events.EventType.KEYDOWN #(reset! last-key (.-keyCode %)))