Orbit

gistfile1.txt

displayMode(FULLSCREEN)
supportedOrientations(PORTRAIT)

function setup()
    D=100 --diameter of planet
    S=120 --speed of planet in pixels per second
    R=math.random(300,1000)--radius of orbit
    a=0 --starting angle for planet
    --set position of centre of sun at bottom
    X=WIDTH/2
    Y=-100
    --calculate planet speed in degrees per redraw
    da=6 * S /  (2 * math.pi * R)
end

function draw()
    background(0)
    local x=X+R*math.sin(math.rad(a)) --turn a into radians for use with math.sin
    local y=Y+R*math.cos(math.rad(a))
    pushStyle()
    --draw the sun
    fill(255,255,0)
    ellipse(X,Y,X+50) -- make the sun peek over the bottom of the screen
    --draw the planet
    fill(209, 168, 92, 255)
    ellipse(x,y,D)
    --reverse direction if we hit the sides
    if x<D/2 or x>WIDTH-D/2 or y<D/2 then da=-da end
    --update the planet angle
    a=a+da
    fontSize(24)
    fill(255)
    text("Restart (circular icon at bottom) to see different orbits",WIDTH/2,HEIGHT-100)
    popStyle()
end