Original code by http://www.lostdecadegames.com/how-to-make-a-simple-html5-canvas-game/

Translated to spanish by Xavier Aznar at http://self_loving.blogspot.com/2013/01/como-crear-un-sencillo-juego-con.html

Modifications:
-Don't reset hero position by Drew Long http://www.lostdecadegames.com/how-to-make-a-simple-html5-canvas-game/#comment-606684891
-Toroidal board by Ryan Kane http://www.lostdecadegames.com/how-to-make-a-simple-html5-canvas-game/#comment-595012625

My additions:
+ Constants (improve legibility)
+ Monster runs from hero
+ Monster increases speed based on monstersCaught (so it gets difficult to catch new monsters)
+ Tombstones mark where monsters has been caught by the hero