Split into separate files for handling
gravity & jumping reversed

more true to life - now jumping is a constant (initial) force, and
gravity accelerates from start of falling
falling smoothness fixed
Added special conditions

Exit & deadliness added to objects.
Also neatened up various bits

Pushing objects of lower hardness is now broken - should fix this
Pushing objects now possible

Touching is only marked on o1 so that o2 can be pushed around (since
it's being pushed around anyway)
img tag added to objects

allows objects to have images as background rather than static colours
added some images