particles from emitter

particles1.lua

-- A converted javascript (by Keith Peters) adapted for Codea by Bri_G
-- ref. http://www.bit-101.com/blog/?p=3150
-- excellent description given 

-- Use this function to perform your initial setup
function setup()
    -- initialisations of system and variables used
    displayMode(FULLSCREEN)
    numPoints = 300 
    gravity = 0.1
    
    points = {x={}, y={}, vx={}, vy={}, radius={}, length={}, colr={}}
    wide = WIDTH
    height = HEIGHT 
    emitterX = wide/2
    emitterY = 800
        
    initPoint(#points.x + 1)
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(0, 0, 0, 255)
    -- This sets the line thickness
    strokeWidth()
    -- Do your drawing here
        fill(29, 181, 212, 255)
    len = #points.x
    for i = 1, len do
        fill(points.colr[i])  
        ellipse(points.x[i], points.y[i], points.radius[i], points.radius[i])
    end
    addPoint()
    update()
end

function update() 
    len = #points.x
    for i = 1, len do
        points.vy[i] = points.vy[i] - gravity
        points.x[i] = points.x[i] + points.vx[i]
        points.y[i] = points.y[i] + points.vy[i]
        if (points.x[i] > wide or points.x[i] < 0 or points.y[i] > height or points.y[i] < 0) then
        initPoint(i)
        end
    end
end

function addPoint() 
    if #points.x < numPoints then
        initPoint(#points.x + 1)
    end
end
    
function initPoint(i)
    points.x[i] = emitterX
    points.y[i] = emitterY
    points.vx[i] = math.random(4) - 2
    points.vy[i] = math.random(5) - 2
    points.radius[i] = math.random(10) + 1
    points.colr[i] = color(math.random(50,200),math.random(50,200),math.random(50,200),255)
end