--Create a window
window = Window:Create()
context = Context:Create(window)
world = World:Create()
camera = Camera:Create()
camera:Move(0,0,-3)
local light = DirectionalLight:Create()
light:SetRotation(35,35,0)

--Create an emitter
emitter = Emitter:Create(100) 

emitter:ClearAlphaControlPoints() --Remove default control points

emitter:AddAlphaControlPoint(0,0)  --at spawn the particle will have an alpha of 0 (fully transparent)
emitter:AddAlphaControlPoint(.5,1)  --halfway through the particle's lifetime alpha will be 1 (ie not transparent)
emitter:AddAlphaControlPoint(1,0)  --at death the particle will be fully transparent

while true do
    if window:Closed() or window:KeyHit(Key.Escape) then return false end

    Time:Update()
    world:Update()
    world:Render()

    --if the space key is pressed all alpha control points are removed
    if (window:KeyDown(Key.Space)) then emitter:ClearAlphaControlPoints() end 

    context:Sync()
end