Change how recording is started

src/play_clj/core.clj

@@ -64,11 +64,11 @@
 (defn ^:private add-to-timeline!
   [screen-atom entities]
   (let [screen @screen-atom]
-    (when (:record? screen)
+    (when (:timeline screen)
       (swap! screen-atom
              update-in
              [:timeline]
-             #(conj (or %1 []) %2)
+             conj
              [(:total-time screen) entities]))))
 
 (defn defscreen*

src/play_clj/core_utils.clj

@@ -80,8 +80,8 @@ specified path.
 
 (defn rewind!
   "Returns the most recent entities vector saved in the timeline after removing
-the last `steps` from it. The timeline is recorded by calling
-`(update! screen :record? true)`.
+the last `steps` from it. Start recording to the timeline by calling
+`(update! screen :timeline [])`.
 
 If there are 100 items saved in the timeline and `(rewind! screen 1)` is called,
 it will remove the last one and return the entities vector from the 99th item.