updated help

public/help.html

@@ -55,6 +55,7 @@
 					<li><em>Fruits</em> give you one point and make you grow. In arcade gamemodes, they also make the game go faster</li>
 					<li><em>Holes</em> kill you if the entire snake is over a hole, or the head and 3 subsequent tiles are over a hole</li>
 					<li><em>Fire</em> kills you if you touch it</li>
+					<li><em>Oil</em> is flammable and will periodically catch on fire, which will kill you. It is otherwise perfectly safe</li>
 					<li><em>Super fruits</em> give you 10 points, and sometimes spawn in arcade mode</li>
 					<li><em>Decaying fruits</em> give you 5 points and sometimes spawn in arcade mode, but they also decay after 2 seconds and disappear</li>
 				</ul>