this.phys = physics.kinematic;
this.dir_view2world = function(dir) { return dir.scale(this.realzoom()); };
this.view2world = function(pos) { return render.view2world(pos); };
this.world2view = function(pos) { return render.world2view(pos); };
this.realzoom = function() { return render.get_zoom(); };

this.screenright = function() { return this.pos.x + (window.rendersize.x/2); }
this.screenleft = function() { return this.pos.x - (window.rendersize.x/2); }

this.zoom = 1;