diff --git a/src/main.moon b/src/main.moon
index 1cd53cd..63def25 100644
--- a/src/main.moon
+++ b/src/main.moon
@@ -1,5 +1,9 @@
 import random from love.math
 
+w, h = love.graphics.getDimensions!
+world = love.physics.newWorld!
+particles = {}
+
 types = setmetatable {}, {
   __index: (t, k) ->
     t[k] = {
@@ -11,25 +15,19 @@ types = setmetatable {}, {
     return t[k]
 }
 
-class Particle
-  new: (@x, @y, @vx, @vy, mass) =>
-    for stat, value in pairs types[mass]
-      @[stat] = value
-  update: (dt) =>
-    @x += @vx * dt
-    @y += @vy * dt
+mk_particle = (x, y, vx, vy, mass) ->
+  stats = types[mass]
+  shape = love.physics.newCircleShape stats.radius
+  body = love.physics.newBody world, x, y, "dynamic"
+  body\setMass stats.mass
+  body\applyForce stats.mass * vx, stats.mass * vy
+  fixture = love.physics.newFixture body, shape
+  particle = setmetatable{ :body, :fixture }, { __index: stats }
+  table.insert particles, particle
 
-particles = {}
-
---   2   2 -- repel 4 (2 - 2 = 0)
---   2  -2 -- attract 4 (2 - -2 = 4)
---   -2  2 -- attract 4 (-2 - 2 = -4)
---   -2 -2 -- repel 4 (-2 - -2 = 0)
--- add abs values
-
-do_physics = (A, B, dt) ->
-  dx = A.x - B.x
-  dy = A.y - B.y
+do_physics = (A, B) ->
+  dx = A.body\getX! - B.body\getX!
+  dy = A.body\getY! - B.body\getY!
   d2 = dx * dx + dy * dy
   a = math.atan2 dy, dx
   x = math.cos a
@@ -40,23 +38,32 @@ do_physics = (A, B, dt) ->
   c *= -1 if (A.charge < 0 and B.charge > 0) or (A.charge > 0 and B.charge < 0)
   f = g + c
 
-  A.vx -= f * x * dt
-  A.vy -= f * y * dt
-  B.vx += f * x * dt
-  B.vy += f * y * dt
+  A.body\applyForce -f * x, -f * y
+  B.body\applyForce f * x, f * y
+
+-- a screen-sized box to keep everything contained
+edges = {
+  left: love.physics.newEdgeShape 0, 0, 0, h
+  right: love.physics.newEdgeShape w, 0, w, h
+  top: love.physics.newEdgeShape 0, 0, w, 0
+  bottom: love.physics.newEdgeShape 0, h, w, h
+}
+edgeBody = love.physics.newBody world, 0, 0
+for _, edge in pairs edges
+  love.physics.newFixture edgeBody, edge
 
 love.update = (dt) ->
   for i = 1, #particles - 1
     for j = i + 1, #particles
       a, b = particles[i], particles[j]
-      do_physics a, b, dt
-      a\update dt
-      b\update dt
+      do_physics a, b
+
+  world\update dt
 
 love.draw = ->
   for particle in *particles
     love.graphics.setColor particle.color
-    love.graphics.circle "fill", particle.x, particle.y, particle.radius
+    love.graphics.circle "fill", particle.body\getX!, particle.body\getY!, particle.radius
 
 love.mousepressed = (x, y, btn) ->
-  table.insert particles, Particle(x, y, 0, 0, math.floor 100 * random!)
+  mk_particle x, y, 0, 0, math.floor 1 + 99 * random!