mvid={}
mvrx={}
mvry={}

rindex=0

function updatevars()
   x = tpt.get_property("x", centerpt)
   y = tpt.get_property("y", centerpt)
end

function particles()
   PT_CD()
   add_particle(x,y)
   if rindex > 0 then
      for tmpid = 1, rindex, 1 do
         add_particle(x - mvrx[tmpid], y - mvry[tmpid])
         tpt.set_property("x", x - mvrx[tmpid], mvid[tmpid])
         tpt.set_property("y", y - mvry[tmpid], mvid[tmpid])
         tpt.set_property("vx", tpt.get_property("vx", centerpt), mvid[tmpid])
         tpt.set_property("vy", tpt.get_property("vy", centerpt), mvid[tmpid])
      end
   end
   if tpt.get_property("type", centerpt) == 116 then reset_moving() end
end

function add_particle(CDx, CDy)
   if tpt.get_property("type", CDx, CDy - 1) == 1 then add_particle_sub(CDx, CDy - 1) end
   if tpt.get_property("type", CDx + 1, CDy - 1) == 1 then add_particle_sub(CDx + 1, CDy - 1) end
   if tpt.get_property("type", CDx + 1, CDy) == 1 then add_particle_sub(CDx + 1, CDy) end
   if tpt.get_property("type", CDx + 1, CDy + 1) == 1 then add_particle_sub(CDx + 1, CDy + 1) end
   if tpt.get_property("type", CDx, CDy + 1) == 1 then add_particle_sub(CDx, CDy + 1) end
   if tpt.get_property("type", CDx - 1, CDy + 1) == 1 then add_particle_sub(CDx - 1, CDy + 1) end
   if tpt.get_property("type", CDx - 1, CDy) == 1 then add_particle_sub(CDx - 1, CDy) end
   if tpt.get_property("type", CDx - 1, CDy - 1) == 1 then add_particle_sub(CDx - 1, CDy - 1) end
   if tpt.get_property("type", CDx, CDy) == 102 then tpt.drawpixel(CDx, CDy, 0, 192, 127, 127) end
end

function PT_CD()
   if x ~= tpt.get_property("x", centerpt) then
      if y ~= tpt.get_property("y", centerpt) then
         errors = 0
         if rindex > 0 then
            for tmpid = 1, rindex, 1 do
               CDx = x - mvrx[tmpid]
               CDy = y - mvry[tmpid]
               if tpt.get_property("type", CDx, CDy - 1) ~= 0 then if tpt.get_property("type", CDx, CDy - 1) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx + 1, CDy - 1) ~= 0 then if tpt.get_property("type", CDx + 1, CDy - 1) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx + 1, CDy) ~= 0 then if tpt.get_property("type", CDx + 1, CDy) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx + 1, CDy + 1) ~= 0 then if tpt.get_property("type", CDx + 1, CDy + 1) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx, CDy + 1) ~= 0 then if tpt.get_property("type", CDx, CDy + 1) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx - 1, CDy + 1) ~= 0 then if tpt.get_property("type", CDx - 1, CDy + 1) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx - 1, CDy) ~= 0 then if tpt.get_property("type", CDx - 1, CDy) ~= 102 then errors = 1 end end
               if tpt.get_property("type", CDx - 1, CDy - 1) ~= 0 then if tpt.get_property("type", CDx - 1, CDy - 1) ~= 102 then errors = 1 end end
            end
         end
         if errors == 1 then tpt.set_property("x", x, centerpt) tpt.set_property("y", y, centerpt) updatevars() end
      end
   end
end

function add_particle_sub(apx, apy)
   rindex = rindex + 1
   tpt.delete(apx, apy)
   mvid[rindex] = tpt.create(apx, apy, "grav")
   mvrx[rindex] = x - apx
   mvry[rindex] = y - apy
end

function reset_moving()
   if rindex > 0 then
      for tmpid = 1, rindex, 1 do
         tpt.delete(tmpid)
      end
      rindex = 0
   end
   tpt.unregister_step(particles)
   tpt.register_mouseevent(click)
end

function click(x, y)
   if tpt.get_property("type",x, y) == 1 then
      tpt.delete(x, y)
    -- Setting up
      centerpt = tpt.create(x, y, "grav")

      mvid={}
      mvrx={}
      mvry={}

      rindex=0
      updatevars()
    -- Setup Complete!
      tpt.register_step(particles)
      tpt.unregister_mouseevent(click)
   end
end

tpt.register_mouseevent(click)