Beginning to build a browser game in Clojure

4 months ago 5

I’m new to Clojure. I asked my new friend Timothy how to make a square appear on the screen:

^:kind/hiccup [:svg [:rect {:width 50 :height 50}]]

Compared to HTML:

It’s nice to not have to close tags, but I’m not sure about the colons, nor the dependencies.

Dependencies aside, we are this square. And we want to be able to move. Timothy, how can I move?

We’ll separate the position data from the rendering:

(def world (atom {:player {:x 75 :y 75}}))

(defn render [world] ^:kind/hiccup [:svg {:style {:border "1px solid black"}} (for [[_entity-id {:keys [x y]}] world] [:rect {:width 50 :height 50 :x x :y y}])])

We’ll add an enemy to see how to work with atom:

(swap! world assoc :enemy {:x 130 :y 75})

{:player {:x 75, :y 75}, :enemy {:x 130, :y 75}}

Let us be different shapes:

(defn render [world] ^:kind/hiccup [:svg {:style {:border "1px solid black"}} (for [[entity-id {:keys [x y]}] world] (if (= entity-id :player) [:rect {:width 50 :height 50 :fill "#62b133" :x x :y y :id "player"}] [:circle {:r 25 :fill "#5880d9" :cx x :cy y :id "enemy"}]))])

Now would be a perfect time to use Reagent to connect the user’s keyboard to our world atom. However, I couldn’t get it working with Clay (what we’re using to render this page). The dependencies have won the first battle.

Moving on, we’ll resort to a script element. Clay lets us use JavaScript, but I couldn’t get it to work with curly braces. Suffering a one-liner, we can now move, via WASD on our keyboard.

^:kind/hiccup [:script #"document.addEventListener('keydown', e => (['w', 'W'].includes(e.key) && player.setAttribute('y', parseInt(player.getAttribute('y')) - 10) || ['a', 'A'].includes(e.key) && player.setAttribute('x', parseInt(player.getAttribute('x')) - 10) || ['s', 'S'].includes(e.key) && player.setAttribute('y', parseInt(player.getAttribute('y')) + 10) || ['d', 'D'].includes(e.key) && player.setAttribute('x', parseInt(player.getAttribute('x')) + 10)))"]

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Beginning to build a browser game in Clojure

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