deletions | additions       diff --git a/figures/three/index3.html b/figures/three/index3.html  index 2eb0d78..7675cce 100644  --- a/figures/three/index3.html  +++ b/figures/three/index3.html 
...
var geometry, material, mesh;  var gravity = 1.0;  var ground_position = -400; -300;  var half_world_width = 500;  var simulation_stopped = true; 
...
if( (mesh.position.y < ground_position)|| (mesh.position.y > -ground_position)  ){ mesh.speed.y = -mesh.speed.y;  }  else{