added class for motion detector
changed css - made energy appear on screen when obstacle triggered
Added motion detector and changed dog so it bites you if you stay too
long
Added alert graphic when obstacle triggered
New obstacle icons, Motion Detector movement trigger changed to 10 m
Added scaling of obstacles although they don't scale a great deal
Attack Screen redesign, using em for font-size, energy bar added
Changed guard behaviour - guard has vision of 60 degrees and turns 60
degrees each location change.  If the user is within the field of vision
and within 10m of the guard the user will lose energy.  Vision is based
on 360 degrees