Update unit4.ipynb

notebooks/unit4/unit4.ipynb

@@ -1357,8 +1357,8 @@
         "- next blocks bottom y location\n",
         "\n",
         "The action space(2) 🎮:\n",
-        "- Up\n",
-        "- Down\n",
+        "- Up (press accelerator) \n",
+        "- Do nothing (don't press accelerator) \n",
         "\n",
         "The reward function 💰: \n",
         "- For each vertical block it passes through it gains a positive reward of +1. Each time a terminal state reached it receives a negative reward of -1."
@@ -1620,4 +1620,4 @@
   },
   "nbformat": 4,
   "nbformat_minor": 0
-}
+}