Circle Collision.lua

-- Copyright Matthew Murdoch
-- Remix under the terms of the MIT license (see http://opensource.org/licenses/MIT)

bounds = nil
circles = {}
    
function setup()
    displayMode(FULLSCREEN)
    physics.gravity(0, 0)
    addBounds()
end

function addBounds()
    bounds = physics.body(CHAIN, 
        vec2(50, 50), 
        vec2(WIDTH-50, 50), 
        vec2(WIDTH-50, HEIGHT-50), 
        vec2(50, HEIGHT-50), 
        vec2(50, 50))
    bounds.type = STATIC
    bounds.restitution = 1
end

function addCircle(x, y, vx, vy)
    local radius = 20
    local circle = physics.body(CIRCLE, radius)
    circle.interpolate = true
    circle.sleepingAllowed = false
    circle.x = x
    circle.y = y
    circle.type = DYNAMIC
    circle.restitution = 1
    circle.linearVelocity = vec2(vx, vy)
    circle.info = color(math.random(0, 255), math.random(0, 255), math.random(0, 255))
    local p1 = { radius = math.random(20, 40) }
    local p2 = { radius = math.random(40, 60) }
    tween.path( 4.0, circle, {p1,p2,p1}, {loop=tween.loop.forever} )
    table.insert(circles, circle)
end

function draw()
    background(40, 40, 50)

    strokeWidth(1)
    local points = bounds.points
    for j = 1, #points do
        a = points[j]
        b = points[(j % #points)+1]
        line(a.x, a.y, b.x, b.y)
    end

    strokeWidth(0)
    for _, circle in ipairs(circles) do
        fill(circle.info)
        ellipse(circle.x, circle.y, circle.radius*2)
    end
end

function touched(touch)
    if touch.state == BEGAN then
        local vx = math.random(-200, 200)
        local vy = math.random(-200, 200)
        addCircle(touch.x, touch.y, vx, vy)
    end
end