I saw this topic on another forum and thought I’d try it with Codea. The subject is calculating the value of Pi by counting the number of collisions using 2 balls and a wall. What this program shows is a red ball moving towards a blue ball. I count the number of collisions that the blue ball has with the wall and the red ball. That count gives the value of Pi. Using M1 mass of 100 and M2 mass of 1, I can only get Pi to 1 decimal position. To get 2 positions, M1 has to be 1,000. 3 positions, M1 has to be 10,000, etc. The Codea Physics engine doesn’t work right if I use M1 mass with 1,000 or higher. That’s just too much of a mass difference between the 2 balls. This example for 1 digit is sufficient to show how this works. For more info, do a Google search on “Playing pool with Pi”.

```
displayMode(FULLSCREEN)
function setup()
physics.continuous=true
cnt=0
pi=0
nbr=2
b1=physics.body(CIRCLE,20)
b1.x=WIDTH
b1.y=140
b1.linearVelocity=vec2(-200,0)
b1.friction=0
b1.restitution=1
b1.info="ball"
b1.mass=10^nbr
b2=physics.body(CIRCLE,20)
b2.x=250
b2.y=140
b2.friction=0
b2.restitution=1
b2.mass=1
e1=physics.body(EDGE,vec2(0,120),vec2(WIDTH,120))
e2=physics.body(EDGE,vec2(0,0),vec2(0,HEIGHT))
e2.info="edge"
end
function draw()
background(40, 40, 50)
noStroke()
fill(255,0,0)
ellipse(b1.x,b1.y,40)
fill(0,0,255)
ellipse(b2.x,b2.y,40)
fill(255)
strokeWidth(2)
stroke(255)
line(0,120,WIDTH,120)
line(0,0,0,HEIGHT)
text("Calculate pi using physics collisions.",WIDTH/2,HEIGHT-100)
text('Do a Google search for "Playing pool with pi".',WIDTH/2,HEIGHT-140)
text("Count = number of blue ball collisions with the wall or red ball.",WIDTH/2,HEIGHT-200)
text("M1 = mass of red ball 100",WIDTH/2,HEIGHT-250)
text("M2 = mass of blue ball 1",WIDTH/2,HEIGHT-280)
text("Count = "..cnt,WIDTH/2,HEIGHT-350)
text("pi = Count/sqrt(M1)",WIDTH/2,HEIGHT-390)
text("pi = "..pi,WIDTH/2,HEIGHT-420)
end
function collide(c)
if c.state==BEGAN then
if c.bodyA.info=="edge" or c.bodyA.info=="ball" then
cnt=cnt+1
pi=cnt/10
end
end
end
```