-- Particles, 2D:  fireworks bursting over the disc, a smoke trail following a moving point, and
-- sparks off a bouncing 2D physics ball, all drawn with the overlay.  Runs without a GPU too.
local font   = fontLoad("Singe/FreeSansBold.ttf", 28)
local frames = 0
local width  = overlayGetWidth()
local height = overlayGetHeight()

fontSelect(font)
discPlay()

-- Fireworks:  a burst of bright additive sparks that fall and fade.
local fireworks = emitterNew()
emitterSetBlend(fireworks, PARTICLE_ADD)
emitterSetLife(fireworks, 0.8, 1.6)
emitterSetSpeed(fireworks, 120, 320)
emitterSetSpread(fireworks, 180)
emitterSetGravity(fireworks, 0, 220)
emitterSetDrag(fireworks, 0.8)
emitterSetSize(fireworks, 14, 3, 0.3)
emitterSetColor(fireworks, 255, 230, 120, 255, 255, 60, 20, 0)
emitterSetMax(fireworks, 2000)

-- Smoke:  grey puffs drifting up from a moving point, drawn under the overlay text.
local smoke = emitterNew()
emitterSetLayer(smoke, PARTICLE_UNDER)
emitterSetRate(smoke, 90)
emitterSetLife(smoke, 1.2, 2.0)
emitterSetSpeed(smoke, 30, 60)
emitterSetDirection(smoke, 0, -1)
emitterSetSpread(smoke, 25)
emitterSetGravity(smoke, 0, -20)
emitterSetSize(smoke, 12, 48, 0.2)
emitterSetColor(smoke, 200, 200, 210, 160, 90, 90, 100, 0)
emitterSetSpin(smoke, -60, 60)
emitterSetRadius(smoke, 6)
emitterStart(smoke)

-- Sparks:  short hot streaks thrown off a ball bouncing in a 2D physics world.
physicsSet2D(true)
physicsSetGravity(0, 600, 0)
local floor = nodeNew()
nodeSetPosition(floor, width / 2, height - 10, 0)
bodyNew(floor, BODY_STATIC, SHAPE_BOX, width, 20, 50)
local ball = nodeNew()
nodeSetPosition(ball, width * 0.25, 80, 0)
bodyNew(ball, BODY_DYNAMIC, SHAPE_SPHERE, 18)
bodySetBounce(ball, 0.8)
bodySetVelocity(ball, 140, 0, 0)
local sparks = emitterNew()
emitterSetBlend(sparks, PARTICLE_ADD)
emitterSetRate(sparks, 160)
emitterSetLife(sparks, 0.3, 0.7)
emitterSetSpeed(sparks, 80, 200)
emitterSetDirection(sparks, 0, -1)
emitterSetSpread(sparks, 70)
emitterSetGravity(sparks, 0, 500)
emitterSetSize(sparks, 5, 1)
emitterSetColor(sparks, 255, 255, 200, 255, 255, 120, 0, 0)
emitterStart(sparks)

local ballSprite = spriteLoad("testScripts/crate.png")

function onOverlayUpdate()
	local t  = frames / 60
	local bx = nodeGetPosition(ball)
	local by = select(2, nodeGetPosition(ball))
	frames = frames + 1
	overlayClear()
	-- The smoke source circles slowly.
	emitterSetPosition(smoke, width / 2 + 160 * math.cos(t), height / 2 + 60 * math.sin(t * 1.3))
	-- Sparks come from wherever the ball is.
	emitterSetPosition(sparks, bx, by + 14)
	if frames % 45 == 1 then
		emitterSetPosition(fireworks, 120 + (frames * 7) % (width - 240), 80 + (frames * 13) % 160)
		emitterBurst(fireworks, 260)
	end
	emitterDraw(smoke)
	emitterDraw(fireworks)
	emitterDraw(sparks)
	spriteDraw(ballSprite, bx - 18, by - 18, bx + 18, by + 18)
	fontPrint(20, 20, "Particles 2D, frame " .. frames .. "  live " .. emitterGetCount(fireworks) + emitterGetCount(smoke) + emitterGetCount(sparks))
	if frames == 40 or frames == 110 or frames == 170 then
		singeScreenshot()
	end
	if frames == 180 then
		singeQuit()
	end
end