title: gravity inside html5 canvas
body: <p>I'm trying to do a copy of the original super mario game using html5 canvas just for fun and to learn more about the canvas tool and it's animation but i am stuck at making Mario do it's jump here is my jsfiddle : <a href="http://jsfiddle.net/2tLCk/1/" rel="nofollow">http://jsfiddle.net/2tLCk/1/</a></p>
  
  <p>how should i fix my <code>up</code> function to make mario jump and return back to the ground like in this website <code>http://blog.nihilogic.dk/</code> i tried to understand it's code but i couldn't ?</p>
  
  <pre><code>if (keydown.up) {
  
              vy += gravity;
              character.CurentPos = 11;
              character.x += character.speed;
              character.y += vy;
  
          }
  </code></pre>