-- Mirrorball:  a demo for Singe, to "Vintage Funky Groove" by miiira.
--
-- A night in a nineties club, in phrases as the song is built:  a choppy intro, the ball coming down
-- over a lit floor, the oldschool effects the dance parties ran on (copper bars, a rotozoomer, a
-- twister, vector bobs, glenz glass, a bouncing checkered ball), a dot cloud, an equalizer city, a
-- turntable, a laser show, a breakdown in the dark, and a party that cuts faster and faster until
-- the ball shatters on the last downbeat.
--
-- The song speeds up as it goes, from about 111 to 117 beats a minute, so nothing here assumes a
-- tempo:  bars and beats come from the beat list in sync.lua, and everything that lands on a beat
-- lands where the drummer put it.
dofile("Singe/Framework.singe")
local K = dofile(DIR .. "../kit.lua")

local FOV         = 60
local TILES       = 12               -- The dance floor is TILES by TILES
local TILE        = 2                -- World units across a tile
local BALL_Y      = 6.2              -- Where the ball hangs
local BALL_R      = 1.45
local FACET       = 0.2
local SPARKLES    = 70               -- Points of light the ball throws on the walls
local LASERS      = 24
local LASER_LEN   = 60               -- How far a beam reaches
local LASER_KINDS = 6                -- Patterns the lasers step through (lasers)
local DOTS        = 320              -- The dot cloud's dots:  32 round by 10 for the torus
local DOT_SHAPES  = 6
local EQ_COLS     = 16               -- The equalizer's bands, left to right ...
local EQ_ROWS     = 12               -- ... and how many moments of history run back from the front ...
local EQ_STEP     = 0.07             -- ... this many seconds apart
local RECORD_R    = 4.5              -- The record on the turntable
local RECORD_RPM  = 33.3
local GROOVES     = 256              -- The record's texture, a side
local RAIN_MAX    = 70               -- Balls that fall on the snares in the boing scene
local TWIST_R     = 92               -- The twister's half width, in pixels
local TWIST_ROW   = 2                -- Screen rows each slice of the twister covers
local ART_DENSITY = 2.25             -- The logo's, the title's, and the bob's pixels to a design unit (util/mirrorballArt.py DENSITY)
local FX_W        = 320              -- The live plasma's and tunnel's size, stretched to wherever they are shown
local FX_H        = 240
local TUNNEL_LAP  = 4                -- The tunnel's travel counts a lap of its texture as this many passes
local PLASMA_STOPS = { { 0.00, { 20, 0, 10 } }, { 0.25, { 150, 20, 40 } }, { 0.50, { 255, 150, 30 } }, { 0.70, { 255, 230, 140 } }, { 0.85, { 255, 255, 255 } }, { 1.00, { 20, 0, 10 } } }
local TUNNEL_STOPS = { { 0.00, { 20, 0, 10 } }, { 0.30, { 150, 20, 40 } }, { 0.55, { 255, 150, 30 } }, { 0.80, { 255, 230, 140 } }, { 1.00, { 255, 255, 255 } } }
local DISCO       = { { 255, 40, 80 }, { 255, 160, 20 }, { 255, 240, 60 }, { 60, 255, 120 }, { 40, 200, 255 }, { 160, 60, 255 } }

local sync  = K.load(DIR)
local W     = K.W                    -- The screen in design units:  480 tall (kit.lua)
local H     = K.H
local art   = {}
local world = {}
local lastT = 0

local SCROLL_TEXT = "MIRRORBALL  ...  A SINGE DEMO  ...  THIS GROOVE SPEEDS UP AS IT GOES, AND EVERY FLASH AND EVERY CUT FOLLOWS IT, BEAT BY BEAT  ..."
local SECOND_TEXT = "COPPER BARS, A ROTOZOOMER, A TWISTER DRAWN ONE SCANLINE AT A TIME, AND GLENZ GLASS  ...  THE OLD TRICKS, ON A NEW ENGINE  ..."
local PARTY_TEXT  = "GREETINGS TO EVERYONE ON THE DANCE FLOOR  ...  KEEP IT FUNKY  ...  MIRRORBALL  ...  A SINGE DEMO  ..."


-- Loading --------------------------------------------------------------------------------------------

local function loadArt()
	for _, name in ipairs({ "twister", "copper", "glow", "sparkle" }) do
		art[name] = spriteLoad(DIR .. "art/" .. name .. ".png")
	end
	for _, name in ipairs({ "logo", "singe", "bob" }) do
		art[name] = K.sprite(DIR .. "art/" .. name .. ".png", ART_DENSITY)
	end
	spriteQuality(art.logo, RENDER_SMOOTH)
	spriteQuality(art.singe, RENDER_SMOOTH)
	art.font  = K.font(44)
	-- The plasma and the tunnel, worked out live in Lua a frame at a time.
	art.plasma = K.plasmaNew(FX_W, FX_H, PLASMA_STOPS)
	art.tunnel = K.tunnelNew(FX_W, FX_H, TUNNEL_STOPS)
end


-- The world --------------------------------------------------------------------------------------------

local function buildFloor()
	local tileImage = spriteLoad(DIR .. "art/tile.png")
	local mesh      = meshBox(TILE * 0.96, 0.2, TILE * 0.96)

	world.tiles = {}
	for i = 1, TILES do
		for j = 1, TILES do
			local m = materialNew()
			local n = nodeNew()

			materialSetColor(m, 40, 30, 50)
			materialSetEmissiveMap(m, tileImage)
			materialSetRoughness(m, 0.2)
			materialSetMetallic(m, 0.3)
			nodeSetMesh(n, mesh, m)
			nodeSetPosition(n, (i - TILES / 2 - 0.5) * TILE, -0.1, (j - TILES / 2 - 0.5) * TILE)
			world.tiles[#world.tiles + 1] = { node = n, material = m, i = i, j = j }
		end
	end
	-- One static body under them all for whatever falls, and walls round the edge to keep it on.
	world.floorBody = nodeNew()
	nodeSetPosition(world.floorBody, 0, -0.2, 0)
	bodyNew(world.floorBody, BODY_STATIC, SHAPE_BOX, TILES * TILE, 0.2, TILES * TILE)
	local half = TILES * TILE / 2

	for _, wall in ipairs({ { half, 0, 0.5, TILES * TILE }, { -half, 0, 0.5, TILES * TILE }, { 0, half, TILES * TILE, 0.5 }, { 0, -half, TILES * TILE, 0.5 } }) do
		local n = nodeNew()

		nodeSetPosition(n, wall[1], 2, wall[2])
		bodyNew(n, BODY_STATIC, SHAPE_BOX, wall[3], 4, wall[4])
	end
end


-- The ball:  facets in rings of latitude round a dark core, all one mesh and one material so they
-- draw in one call, on a pivot that turns.  Each facet faces out from the centre.
local FACET_GROUPS = 4

local function buildBall()
	local mesh = meshBox(FACET * 0.92, FACET * 0.92, 0.04)

	-- Facets in four groups, each its own material, so each group can catch the light in turn:  a
	-- real ball's facets flash as they come round to a lamp.  Four materials still draw in four calls.
	world.facetMaterials = {}
	for g = 1, FACET_GROUPS do
		world.facetMaterials[g] = K.chrome(200 + g * 10, 205 + g * 8, 225, 0.06 + g * 0.03)
	end
	world.ball = nodeNew()
	world.facets = {}
	local rings = math.floor(math.pi * BALL_R / FACET)

	for r = 1, rings - 1 do
		local lat   = -math.pi / 2 + r / rings * math.pi
		local count = math.max(4, math.floor(2 * math.pi * BALL_R * math.cos(lat) / FACET))

		for c = 0, count - 1 do
			local lon = (c + (r % 2) * 0.5) / count * 2 * math.pi
			local f   = nodeNew(world.ball)
			local x   = math.cos(lat) * math.cos(lon) * BALL_R
			local y   = math.sin(lat) * BALL_R
			local z   = math.cos(lat) * math.sin(lon) * BALL_R

			nodeSetMesh(f, mesh, world.facetMaterials[math.random(1, FACET_GROUPS)])
			nodeSetPosition(f, x, y, z)
			nodeLookAt(f, 0, 0, 0)
			world.facets[#world.facets + 1] = { node = f, x = x, y = y, z = z }
		end
	end
	local core = materialNew()

	materialSetColor(core, 10, 10, 14)
	world.core = nodeNew(world.ball)
	nodeSetMesh(world.core, meshSphere(BALL_R - 0.03, 24), core)
	local rope = materialNew()

	materialSetColor(rope, 30, 30, 34)
	world.rope = nodeNew()
	nodeSetMesh(world.rope, meshCylinder(0.03, 12, 6), rope)
	nodeSetPosition(world.ball, 0, BALL_Y, 0)

	-- The light the ball throws:  sparkles on a great sphere round it, turning with it.
	world.sparkleRing = nodeNew()
	nodeSetPosition(world.sparkleRing, 0, BALL_Y, 0)
	world.sparkles = {}
	for i = 1, SPARKLES do
		local phi   = math.acos(1 - 2 * (i - 0.5) / SPARKLES) * 0.75
		local theta = math.pi * (1 + math.sqrt(5)) * i
		local n     = nodeNew(world.sparkleRing)

		nodeSetSprite(n, art.sparkle, 1.8, false)
		nodeSetBillboard(n, BILLBOARD_ALL)
		nodeSetPosition(n, math.cos(theta) * math.sin(phi + 0.6) * 16, -math.cos(phi + 0.6) * 9, math.sin(theta) * math.sin(phi + 0.6) * 16)
		world.sparkles[i] = n
	end
end


local function buildLights()
	world.spots = {}
	for i = 1, 4 do
		local l = lightNew(LIGHT_SPOT)
		local c = DISCO[i + 1]

		lightSetColor(l, c[1], c[2], c[3])
		lightSetIntensity(l, 0)
		lightSetRange(l, 60)
		lightSetCone(l, 10, 18)
		world.spots[i] = l
	end
	world.ballSpot = lightNew(LIGHT_SPOT)
	nodeSetPosition(world.ballSpot, 0, 14, 8)
	nodeLookAt(world.ballSpot, 0, BALL_Y, 0)
	lightSetColor(world.ballSpot, 255, 250, 240)
	lightSetIntensity(world.ballSpot, 0)
	lightSetCone(world.ballSpot, 5, 9)
	world.sun = lightNew(LIGHT_DIRECTIONAL)
	nodeSetPosition(world.sun, 4, 10, 6)
	nodeLookAt(world.sun, 0, 0, 0)
	lightSetIntensity(world.sun, 0)
	lightSetShadow(world.sun, true)
end


-- Lasers:  thin bright rods, each on an arm placed and aimed every frame by the pattern (lasers),
-- in the club's colours.  The rod hangs off its arm's -Z, the way nodeLookAt points.
local function buildLasers()
	local mesh = meshBox(1, 1, LASER_LEN)

	world.laserMaterials = {}
	for i, c in ipairs(DISCO) do
		local m = materialNew()

		materialSetColor(m, 0, 0, 0)
		materialSetEmissive(m, c[1], c[2], c[3])
		world.laserMaterials[i] = m
	end
	world.laserFan = nodeNew()
	world.lasers = {}
	for i = 1, LASERS do
		local arm = nodeNew(world.laserFan)
		local rod = nodeNew(arm)

		nodeSetMesh(rod, mesh, world.laserMaterials[i % #DISCO + 1])
		nodeSetPosition(rod, 0, 0, -LASER_LEN / 2)
		nodeSetShadow(rod, false)
		world.lasers[i] = { arm = arm, rod = rod }
	end
end


-- Glenz vectors:  a glass octahedron inside a glass cube, both faceted, turning against each other.
local function octahedron(r)
	local v = { { r, 0, 0 }, { -r, 0, 0 }, { 0, r, 0 }, { 0, -r, 0 }, { 0, 0, r }, { 0, 0, -r } }
	local faces = { { 1, 3, 5 }, { 5, 3, 2 }, { 2, 3, 6 }, { 6, 3, 1 }, { 5, 4, 1 }, { 2, 4, 5 }, { 6, 4, 2 }, { 1, 4, 6 } }
	local positions = {}
	local normals   = {}
	local indices   = {}

	for _, f in ipairs(faces) do
		local a = v[f[1]]
		local b = v[f[2]]
		local c = v[f[3]]
		local nx = (a[1] + b[1] + c[1]) / 3
		local ny = (a[2] + b[2] + c[2]) / 3
		local nz = (a[3] + b[3] + c[3]) / 3
		local l  = math.sqrt(nx * nx + ny * ny + nz * nz)

		for _, p in ipairs({ a, b, c }) do
			positions[#positions + 1] = p[1]
			positions[#positions + 1] = p[2]
			positions[#positions + 1] = p[3]
			normals[#normals + 1]     = nx / l
			normals[#normals + 1]     = ny / l
			normals[#normals + 1]     = nz / l
			indices[#indices + 1]     = #positions / 3
		end
	end
	return meshNew(positions, normals, nil, indices)
end


local function buildGlenz()
	world.glenz = nodeNew()
	world.glenzOuter = nodeNew(world.glenz)
	world.glenzInner = nodeNew(world.glenz)
	local outer = K.glass(255, 60, 200, 110)
	local inner = K.glass(60, 220, 255, 150)

	materialSetDoubleSided(outer, true)
	materialSetEmissive(outer, 70, 12, 60)
	materialSetEmissive(inner, 12, 60, 75)
	nodeSetMesh(world.glenzOuter, meshBox(2.4, 2.4, 2.4), outer)
	nodeSetMesh(world.glenzInner, octahedron(1.25), inner)
end


-- The boing ball, and the balls that rain on the snares.
local function buildBoing()
	local skin = materialNew()

	materialSetTexture(skin, spriteLoad(DIR .. "art/boing.png"))
	materialSetRoughness(skin, 0.35)
	world.boing = nodeNew()
	nodeSetMesh(world.boing, meshSphere(1.6, 32), skin)
	world.rainMesh = meshSphere(0.32, 16)
	world.rainMaterials = {}
	for i, c in ipairs(DISCO) do
		local m = materialNew()

		materialSetColor(m, c[1], c[2], c[3])
		materialSetMetallic(m, 0.4)
		materialSetRoughness(m, 0.2)
		world.rainMaterials[i] = m
	end
	world.rain = {}
end


-- Screens for the 2D-in-3D effects:  the rotozoomer, the tunnel, and a kaleidoscope of four mirrored
-- copies of the plasma.
local function buildScreens()
	local roto = materialNew()

	materialSetTexture(roto, spriteLoad(DIR .. "art/roto.png"))
	materialSetUnlit(roto, true)
	materialSetDoubleSided(roto, true)
	materialSetFilter(roto, FILTER_NEAREST)
	world.rotoMaterial = roto
	world.roto = K.screenQuad(world.camera, FOV, roto, 2, true)
	local tunnel = materialNew()

	world.tunnelMaterial = tunnel
	materialSetTexture(tunnel, art.tunnel.sprite)
	materialSetUnlit(tunnel, true)
	materialSetDoubleSided(tunnel, true)
	world.tunnel = K.screenQuad(world.camera, FOV, tunnel, 60, true)
	world.kaleido = nodeNew(world.camera)
	world.kaleidoMaterials = {}
	nodeSetPosition(world.kaleido, 0, 0, -2)
	local h = 2 * 2 * math.tan(math.rad(FOV / 2))
	local w = h * W / H

	for _, q in ipairs({ { -1, 1, 1, 1 }, { 1, 1, -1, 1 }, { -1, -1, 1, -1 }, { 1, -1, -1, -1 } }) do
		local m = materialNew()
		local n = nodeNew(world.kaleido)

		materialSetTexture(m, art.plasma.sprite)
		world.kaleidoMaterials[#world.kaleidoMaterials + 1] = m
		materialSetUnlit(m, true)
		materialSetDoubleSided(m, true)
		materialSetTiling(m, q[3], q[4])
		nodeSetMesh(n, meshPlane(w / 2, h / 2), m)
		nodeSetPosition(n, q[1] * w / 4, q[2] * h / 4, 0)
		nodeSetRotation(n, 90, 0, 0)
	end
end


-- The dot cloud:  glowing dots that gather into a new shape on every bar.  Each shape is worked out
-- once, a point per dot.
local function dotShape(shape, i)
	local f = (i - 0.5) / DOTS

	if shape == 0 then
		-- A sphere, the dots spread evenly by the golden angle.
		local y = 1 - 2 * f
		local r = math.sqrt(1 - y * y)
		local a = i * 2.39996

		return math.cos(a) * r * 3, y * 3, math.sin(a) * r * 3
	elseif shape == 1 then
		-- A torus, 32 round and 10 about the tube.
		local a = (i % 32) / 32 * 2 * math.pi
		local b = math.floor(i / 32) / 10 * 2 * math.pi

		return (2.6 + math.cos(b)) * math.cos(a), math.sin(b), (2.6 + math.cos(b)) * math.sin(a)
	elseif shape == 2 then
		-- A cube's six faces, a grid on each.
		local k = math.floor((i - 1) / 6)
		local u = (k % 8) / 7 * 2 - 1
		local v = math.floor(k / 8) % 8 / 7 * 2 - 1
		local p = ({ { 1, u, v }, { -1, u, v }, { u, 1, v }, { u, -1, v }, { u, v, 1 }, { u, v, -1 } })[(i - 1) % 6 + 1]

		return p[1] * 2.2, p[2] * 2.2, p[3] * 2.2
	elseif shape == 3 then
		-- Two strands of a helix.
		local k = math.floor((i - 1) / 2)
		local a = k * 0.25 + (i % 2) * math.pi

		return math.cos(a) * 1.8, (k / (DOTS / 2) - 0.5) * 7, math.sin(a) * 1.8
	elseif shape == 4 then
		-- A flower of eight petals, rippling.
		local a = f * 2 * math.pi
		local r = 3.2 * math.cos(4 * a)

		return math.cos(a) * r, 0.8 * math.sin(8 * a), math.sin(a) * r
	end
	-- A flat grid, which the music makes into waves (dotsUpdate).
	return (i % 20) / 19 * 7 - 3.5, 0, math.floor(i / 20) / 15 * 6 - 3
end


local function buildDots()
	local mesh = meshSphere(0.11, 8)

	world.dots          = nodeNew()
	world.dotNodes      = {}
	world.dotMaterials  = {}
	world.dotShapes     = {}
	for i, c in ipairs(DISCO) do
		local m = materialNew()

		materialSetColor(m, 0, 0, 0)
		materialSetEmissive(m, c[1], c[2], c[3])
		world.dotMaterials[i] = m
	end
	for i = 1, DOTS do
		local n = nodeNew(world.dots)

		nodeSetMesh(n, mesh, world.dotMaterials[i % #DISCO + 1])
		nodeSetShadow(n, false)
		world.dotNodes[i] = n
	end
	for shape = 0, DOT_SHAPES - 1 do
		local points = {}

		for i = 1, DOTS do
			points[i] = { dotShape(shape, i) }
		end
		world.dotShapes[shape + 1] = points
	end
end


-- The equalizer:  a city of bars, a band of the music to each column and the last moments of it
-- running back in the rows, so the beat rolls away from the viewer.
local function buildEqualizer()
	local mesh = meshBox(0.8, 1, 0.8)

	world.eq          = nodeNew()
	world.eqBars      = {}
	world.eqMaterials = {}
	for c = 1, EQ_COLS do
		local m = materialNew()

		materialSetColor(m, 20, 20, 30)
		materialSetMetallic(m, 0.6)
		materialSetRoughness(m, 0.25)
		world.eqMaterials[c] = m
		world.eqBars[c] = {}
		for r = 1, EQ_ROWS do
			local n = nodeNew(world.eq)

			nodeSetMesh(n, mesh, m)
			world.eqBars[c][r] = n
		end
	end
end


-- The turntable:  a record of grooves round a red label with the Singe logo on it, on a chrome
-- platter, and a tonearm resting on it.  The grooves are drawn here, a pixel at a time.
local function buildTurntable()
	local grooves = spriteNew(GROOVES, GROOVES)
	local pixels  = {}
	local vinyl   = materialNew()
	local label   = materialNew()
	local black   = materialNew()
	local steel   = K.chrome(200, 200, 210, 0.15)

	for y = 0, GROOVES - 1 do
		for x = 0, GROOVES - 1 do
			local d = math.sqrt((x - GROOVES / 2 + 0.5) ^ 2 + (y - GROOVES / 2 + 0.5) ^ 2) / (GROOVES / 2)
			local v = math.floor(18 + 10 * (0.5 + 0.5 * math.sin(d * 420)))

			if d < 0.34 then
				pixels[#pixels + 1] = (d > 0.32) and string.char(240, 200, 90, 255) or string.char(190, 25, 50, 255)
			else
				-- The gaps between the tracks are smooth, and shine.
				for _, gap in ipairs({ 0.52, 0.68, 0.83 }) do
					if math.abs(d - gap) < 0.008 then
						v = 45
					end
				end
				pixels[#pixels + 1] = string.char(v, v, v + 2, 255)
			end
		end
	end
	spriteSetPixels(grooves, table.concat(pixels))
	materialSetTexture(vinyl, grooves)
	materialSetRoughness(vinyl, 0.3)
	materialSetMetallic(vinyl, 0.2)
	materialSetTexture(label, art.singe)
	materialSetBlend(label, true)
	materialSetUnlit(label, true)
	materialSetColor(black, 6, 6, 8)
	materialSetRoughness(black, 0.25)
	world.vinyl = nodeNew()
	world.record = nodeNew(world.vinyl)
	nodeSetMesh(world.record, K.disc(RECORD_R, 96), vinyl)
	local logo = nodeNew(world.record)
	local w    = RECORD_R * 0.55

	nodeSetMesh(logo, meshPlane(w, w * spriteGetHeight(art.singe) / spriteGetWidth(art.singe)), label)
	nodeSetPosition(logo, 0, 0.01, 0)
	local platter = nodeNew(world.vinyl)

	nodeSetMesh(platter, meshCylinder(RECORD_R + 0.15, 0.3, 64), steel)
	nodeSetPosition(platter, 0, -0.16, 0)
	local plinth = nodeNew(world.vinyl)

	nodeSetMesh(plinth, meshBox(12, 0.8, 11), black)
	nodeSetPosition(plinth, 0.8, -0.72, 0)
	local spindle = nodeNew(world.vinyl)

	nodeSetMesh(spindle, meshCylinder(0.08, 0.4, 12), steel)
	-- The tonearm turns about its post at the back right;  its head rests on the record.
	world.tonearm = nodeNew(world.vinyl)
	nodeSetPosition(world.tonearm, 5.6, 0.55, -3.8)
	local post = nodeNew(world.vinyl)

	nodeSetMesh(post, meshCylinder(0.3, 0.9, 16), steel)
	nodeSetPosition(post, 5.6, 0.1, -3.8)
	local arm = nodeNew(world.tonearm)

	nodeSetMesh(arm, meshBox(0.12, 0.12, 6.4), steel)
	nodeSetPosition(arm, 0, 0, 3.2)
	local head = nodeNew(world.tonearm)

	nodeSetMesh(head, meshBox(0.5, 0.2, 0.9), black)
	nodeSetPosition(head, 0, -0.35, 6.4)
end


local function buildWorld()
	sceneEnable(true)
	sceneSetSky(DIR .. "art/club.png")
	sceneSetSkyIntensity(1.0)
	sceneSetAmbient(20, 16, 30)
	sceneSetBloom(0.7, 0.55)
	world.camera = nodeNew()
	cameraSet(world.camera)
	cameraSetPerspective(FOV, 0.1, 400)
	K.screen(world.camera, FOV, 400)
	buildFloor()
	buildBall()
	buildLights()
	buildLasers()
	buildGlenz()
	buildBoing()
	buildScreens()
	buildDots()
	buildEqualizer()
	buildTurntable()
end


-- What is shown --------------------------------------------------------------------------------------

local function setVisible(list, on)
	for _, n in ipairs(list) do
		nodeSetVisible(n, on)
	end
end


local function hideAll()
	for _, tile in ipairs(world.tiles) do
		nodeSetVisible(tile.node, false)
	end
	setVisible({ world.ball, world.rope, world.sparkleRing, world.laserFan, world.glenz, world.boing, world.roto, world.tunnel, world.kaleido, world.dots, world.eq, world.vinyl }, false)
	for _, l in ipairs(world.spots) do
		lightSetIntensity(l, 0)
	end
	lightSetIntensity(world.ballSpot, 0)
	lightSetIntensity(world.sun, 0)
	sceneSetFog()
	sceneSetSkyIntensity(1.0)
	sceneSetBloom(0.7, 0.55)
end


local function showClub(withBall)
	for _, tile in ipairs(world.tiles) do
		nodeSetVisible(tile.node, true)
	end
	setVisible({ world.ball, world.rope, world.sparkleRing }, withBall ~= false)
end


-- The club in motion ----------------------------------------------------------------------------------

-- The ball turns, hangs at height y, and its sparkles turn with it, twinkling on the hats.
local function ballSpin(t, y, speed, sparkle)
	local spin = t * (speed or 30)

	nodeSetPosition(world.ball, 0, y, 0)
	nodeSetRotation(world.ball, 0, spin, 0)
	nodeSetPosition(world.rope, 0, y + 6, 0)
	nodeSetPosition(world.sparkleRing, 0, y, 0)
	nodeSetRotation(world.sparkleRing, 0, spin, 0)
	local s = (sparkle or 1) * (0.6 + 0.6 * K.env("hat", t))

	for g, m in ipairs(world.facetMaterials) do
		local v = (sparkle or 1) * (40 + 215 * math.max(0, math.sin(t * 9 + g * 1.7)) ^ 6 + 60 * K.decay("kicks", t, 8))

		materialSetEmissive(m, math.floor(math.min(255, v)), math.floor(math.min(255, v)), math.floor(math.min(255, v * 1.05)))
	end
	nodeSetScale(world.sparkleRing, 1)
	for i, n in ipairs(world.sparkles) do
		nodeSetScale(n, s * (0.5 + 0.5 * math.sin(t * 7 + i * 2.3)))
	end
	lightSetIntensity(world.ballSpot, 60 * (sparkle or 1))
end


-- The spotlights sweep the room on circles of their own, flaring on the kicks.
local function spots(t, level)
	local flare = 1 + 1.5 * K.decay("kicks", t, 6)

	for i, l in ipairs(world.spots) do
		local a = t * 0.7 + i * math.pi / 2

		nodeSetPosition(l, math.cos(i * 1.57) * 10, 11, math.sin(i * 1.57) * 10)
		nodeLookAt(l, math.cos(a) * 6, 0, math.sin(a) * 6)
		lightSetIntensity(l, 120 * level * flare)
	end
end


-- The floor's patterns, one per phrase:  a checker that swaps on every beat, ripples from the middle
-- on the kicks, diagonal waves, and a scatter that changes every beat.  level dims it all.
local function floor(t, pattern, level)
	local b       = K.beat(t)
	local whole   = math.floor(b)
	local ripple  = K.hitAge("kicks", t) * 14
	local colour  = DISCO[whole % #DISCO + 1]

	for _, tile in ipairs(world.tiles) do
		local i = tile.i
		local j = tile.j
		local v = 0

		if pattern == 0 then
			v = ((i + j + whole) % 2 == 0) and 1 or 0.08
		elseif pattern == 1 then
			local d = math.sqrt((i - TILES / 2 - 0.5) ^ 2 + (j - TILES / 2 - 0.5) ^ 2) * TILE
			v = math.max(0.06, math.exp(-math.abs(d - ripple) * 0.9))
		elseif pattern == 2 then
			v = 0.5 + 0.5 * math.sin((i + j) * 0.8 - t * 6)
		else
			v = (((i * 7 + j * 13 + whole * 31) % 17) < 6) and 1 or 0.05
		end
		local c = colour

		if pattern == 2 or pattern == 1 then
			c = DISCO[(i + j + whole) % #DISCO + 1]
		end
		v = v * level
		materialSetEmissive(tile.material, math.floor(c[1] * v), math.floor(c[2] * v), math.floor(c[3] * v))
	end
end


-- A repeatable number from 0 to 1 for a pair of numbers, so a pattern lands the same way every run.
local function hash(a, b)
	return (math.sin(a * 12.9898 + b * 78.233) * 43758.5453) % 1
end


-- The lasers, stepping through their patterns perBar times a bar:  a fan sweeping from the back
-- wall, scissors from the two corners, beams thrown off the turning ball, a tunnel round the camera,
-- a sheet that rolls over, and chaos, thrown somewhere new on every snare.  The colours step round on
-- every beat, beams chase on the hats, and they fatten on the kicks and flare on the snares.
local function lasers(t, level, perBar)
	local kind   = math.floor((K.bar(t) - 1) * (perBar or 1)) % LASER_KINDS
	local beat   = K.beat(t)
	local chase  = math.floor(beat * 4)
	local width  = 0.05 + 0.12 * K.decay("kicks", t, 7)
	local glow   = level * (0.6 + 0.4 * K.decay("snares", t, 8))
	local snares = K.hitCount("snares", 0, t)
	local cx, cy, cz = nodeGetWorldPosition(world.camera)

	for i, c in ipairs(DISCO) do
		materialSetEmissive(world.laserMaterials[i], math.floor(c[1] * glow), math.floor(c[2] * glow), math.floor(c[3] * glow))
	end
	for i, beam in ipairs(world.lasers) do
		local f  = (i - 0.5) / LASERS
		local ox = 0
		local oy = 9
		local oz = -16
		local dx = 0
		local dy = 0
		local dz = 1
		local on = true

		if kind == 0 then
			local a = math.rad(math.sin(t * 1.3) * 25 + (f - 0.5) * (110 + 40 * math.sin(t * 0.7)))
			local e = math.rad(-12 + 14 * math.sin(t * 0.9 + i))

			dx = math.sin(a) * math.cos(e)
			dy = math.sin(e)
			dz = math.cos(a) * math.cos(e)
			on = (i + chase) % 3 ~= 0
		elseif kind == 1 then
			local side = (i % 2 == 0) and 1 or -1
			local k    = math.floor((i - 1) / 2)
			local a    = math.rad(-side * (15 + k * 5 + 30 * math.sin(t * 2.4)))
			local e    = math.rad(-8 - 6 * math.sin(t * 3 + k))

			ox = side * 12
			oy = 8
			oz = -12
			dx = math.sin(a) * math.cos(e)
			dy = math.sin(e)
			dz = math.cos(a) * math.cos(e)
		elseif kind == 2 then
			local y = -0.85 + 0.9 * f
			local r = math.sqrt(1 - y * y)
			local a = i * 2.39996 + t * 0.9

			oy = BALL_Y
			oz = 0
			dx = math.cos(a) * r
			dy = y
			dz = math.sin(a) * r
		elseif kind == 3 then
			local a = i / LASERS * 2 * math.pi + t * 0.8

			ox = math.cos(a) * 9
			oy = 5 + math.sin(a) * 6
			oz = -18
			dx = cx + math.cos(a) * 2.5 - ox
			dy = cy + math.sin(a) * 2.5 - oy
			dz = cz - oz
		elseif kind == 4 then
			local p = math.rad((f - 0.5) * 160)
			local r = math.rad(t * 70)

			oy = 10
			dx = math.sin(p) * math.cos(r)
			dy = math.sin(p) * math.sin(r) - 0.25
			dz = math.cos(p)
			on = (i + chase) % 2 == 0
		else
			ox = ((i % 3) - 1) * 12
			oy = 9 + (i % 3 == 1 and 1 or 0)
			oz = -14
			dx = hash(i, snares) * 2 - 1 + 0.1 * math.sin(t * 3 + i)
			dy = -hash(snares, i) * 0.8
			dz = 0.3 + hash(i + 7, snares)
		end
		nodeSetVisible(beam.arm, on)
		nodeSetPosition(beam.arm, ox, oy, oz)
		nodeLookAt(beam.arm, ox + dx, oy + dy, oz + dz)
		nodeSetScale(beam.rod, width, width, 1)
		nodeSetMaterial(beam.rod, world.laserMaterials[(i + math.floor(beat)) % #DISCO + 1])
	end
end


local function orbit(t, radius, height, speed, lookY, phase)
	local a = t * speed + (phase or 0)

	nodeSetPosition(world.camera, math.cos(a) * radius, height, math.sin(a) * radius)
	nodeLookAt(world.camera, 0, lookY, 0)
end


-- 2D effects --------------------------------------------------------------------------------------------

-- Copper bars:  count bars swinging up and down, coloured by hue, each a gradient strip stretched
-- across the screen under the overlay.
local function copperBars(t, count, y0, amp, hueShift, alpha)
	for i = 1, count do
		local y = y0 + math.sin(t * 2.1 + i * 0.55) * amp
		local r, g, b = K.hue(i / count * 0.6 + hueShift)

		K.under(art.copper, 0, y, W, y + 24, r, g, b, alpha)
	end
end


-- The twister:  a square bar turning about the vertical, its turn varying down the screen.  Each
-- scanline shows the faces whose edges come round in order there, each face one row of its texture
-- stretched between its two edges and shaded by how squarely it faces the viewer.
local function twister(t, cx)
	local faceW = 64

	for y = 0, H - 1, TWIST_ROW do
		local a     = t * 1.6 + math.sin(y * 0.011 + t * 1.2) * 2.2 + math.sin(t * 0.5) * y * 0.004
		local row   = math.floor(y + t * 60) % 64
		local x     = {}
		local wobble = math.sin(y * 0.02 + t * 2) * 30

		for e = 0, 4 do
			x[e] = cx + wobble + math.sin(a + e * math.pi / 2) * TWIST_R
		end
		for e = 0, 3 do
			if x[e + 1] > x[e] + 0.5 then
				local shade = math.floor(80 + 175 * math.sin(math.min(math.pi, (x[e + 1] - x[e]) / (2 * TWIST_R) * math.pi * 0.72)))

				spriteSetTint(art.twister, shade, shade, shade)
				K.drawGrid(art.twister, x[e], y, e * faceW, row, faceW, 1, x[e + 1], y + TWIST_ROW)
			end
		end
	end
	spriteSetTint(art.twister, 255, 255, 255)
end


-- The title, a letter at a time:  each falls from above, lands on its beat, and bounces lower each
-- beat after.
local TITLE = "MIRRORBALL"

local function titleDrop(t, firstBeat, beatsApart, y)
	local b      = K.beat(t)
	local widths = {}
	local total  = 0

	for i = 1, #TITLE do
		widths[i] = K.textWidth(TITLE:sub(i, i), 72) + 4
		total     = total + widths[i]
	end
	local x = W / 2 - total / 2

	for i = 1, #TITLE do
		local land = firstBeat + (i - 1) * beatsApart
		local since = b - land

		if since > -1 then
			local lift = 0

			if since < 0 then
				lift = (since * since) * 300
			else
				local bounce = since % 1
				local height = 60 * math.exp(-math.floor(since) * 0.8)

				lift = 4 * height * bounce * (1 - bounce)
			end
			local r, g, bb = K.hue(i / #TITLE + t * 0.05)

			K.text(x + widths[i] / 2, y - lift, TITLE:sub(i, i), 72, r, g, bb, "center")
		end
		x = x + widths[i]
	end
end


-- The shatter -------------------------------------------------------------------------------------------

-- Every facet leaves the ball:  put where it is in the world, given a body, and thrown outward and
-- up with a spin.
local function shatter(t)
	local spin = math.rad(t * world.lastSpin)
	local c    = math.cos(spin)
	local s    = math.sin(spin)
	local by   = world.lastBallY

	nodeSetVisible(world.core, false)
	nodeSetVisible(world.rope, false)
	for _, f in ipairs(world.facets) do
		-- The ball turned about y by spin;  the facet's place in the room follows.
		local x = f.x * c + f.z * s
		local z = -f.x * s + f.z * c

		nodeSetParent(f.node, 0)
		nodeSetPosition(f.node, x, by + f.y, z)
		nodeLookAt(f.node, 0, by, 0)
		bodyNew(f.node, BODY_DYNAMIC, SHAPE_BOX, FACET, FACET, 0.04)
		bodySetMass(f.node, 0.05)
		bodySetBounce(f.node, 0.35)
		local out = 3 + math.random() * 5

		bodySetVelocity(f.node, x / BALL_R * out, (f.y / BALL_R) * out + 3, z / BALL_R * out)
		bodySetAngularVelocity(f.node, (math.random() - 0.5) * 20, (math.random() - 0.5) * 20, (math.random() - 0.5) * 20)
	end
	world.shattered = true
end


-- Scenes placed more than once ---------------------------------------------------------------------
-- Each is a scene table without its bars;  at() gives it them, and a flash of white as it starts.

local EQ_BANDS = { "kick", "kick", "kick", "bass", "bass", "bass", "level", "level", "bright", "bright", "snare", "snare", "snare", "hat", "hat", "hat" }

local function at(from, to, scene)
	local placed = {}
	local start  = K.barTime(from)

	for key, value in pairs(scene) do
		placed[key] = value
	end
	placed.from = from
	placed.to   = to
	placed.draw = function(t, bar, k)
		scene.draw(t, bar, k)
		K.flash(255, 255, 255, math.floor(255 * math.exp(-math.max(0, t - start) * 9)))
	end
	return placed
end


-- The dot cloud gathers into a new shape on every bar, the dots setting off one after another, and
-- swells on the kicks.  The flat grid rides the music as waves.
local DOT_CLOUD = {
	enter = function(t)
		hideAll()
		nodeSetVisible(world.dots, true)
		sceneSetSkyIntensity(0.35)
	end,
	draw = function(t, bar, k)
		local whole  = math.floor(bar)
		local before = (whole - 2) % DOT_SHAPES + 1
		local now    = (whole - 1) % DOT_SHAPES + 1
		local into   = (bar - whole) * 4
		local pulse  = 1 + 0.25 * K.decay("kicks", t, 7)
		local level  = K.env("level", t)
		local glow   = 0.6 + 0.6 * K.env("hat", t)

		for i, n in ipairs(world.dotNodes) do
			local m    = K.ease(K.clamp(into * 1.4 - (i / DOTS) * 0.6, 0, 1))
			local a    = world.dotShapes[before][i]
			local b    = world.dotShapes[now][i]
			local x    = K.lerp(a[1], b[1], m) * pulse
			local z    = K.lerp(a[3], b[3], m) * pulse
			local flat = (before == DOT_SHAPES and 1 - m or 0) + (now == DOT_SHAPES and m or 0)

			nodeSetPosition(n, x, K.lerp(a[2], b[2], m) * pulse + flat * math.sin(x * 1.3 + z * 0.7 + t * 5) * 1.2 * level, z)
		end
		for i, c in ipairs(DISCO) do
			materialSetEmissive(world.dotMaterials[i], math.floor(math.min(255, c[1] * glow)), math.floor(math.min(255, c[2] * glow)), math.floor(math.min(255, c[3] * glow)))
		end
		nodeSetPosition(world.dots, 0, 2.5, 0)
		nodeSetRotation(world.dots, 20 * math.sin(t * 0.5), t * 40, 0)
		nodeSetPosition(world.camera, 0, 3.2, 7.5)
		nodeLookAt(world.camera, 0, 2.5, 0)
		K.strobe(t, "kicks", 14, 255, 255, 255, 30)
	end,
}


-- The equalizer city, flown over low:  each column a band of the music, each row the same band a
-- moment earlier, coloured round the wheel and lit by how loud the front row is.
local EQUALIZER = {
	enter = function(t)
		hideAll()
		nodeSetVisible(world.eq, true)
		sceneSetSkyIntensity(0.7)
		lightSetIntensity(world.sun, 3)
	end,
	draw = function(t, bar, k)
		for c = 1, EQ_COLS do
			local band  = EQ_BANDS[c]
			local tilt  = 0.75 + 0.25 * math.sin(c * 1.7)
			local front = K.env(band, t) * tilt
			local cr, cg, cb = K.hue(c / EQ_COLS * 0.8 + t * 0.05)
			local g     = 0.2 + 0.9 * front

			for r = 1, EQ_ROWS do
				local h = 0.15 + 5.5 * K.env(band, t - (r - 1) * EQ_STEP) * tilt
				local n = world.eqBars[c][r]

				nodeSetPosition(n, c - EQ_COLS / 2 - 0.5, h / 2, -(r - 1))
				nodeSetScale(n, 1, h, 1)
			end
			materialSetEmissive(world.eqMaterials[c], math.floor(math.min(255, cr * g)), math.floor(math.min(255, cg * g)), math.floor(math.min(255, cb * g)))
		end
		nodeSetPosition(world.camera, math.sin(t * 0.35) * 8, 3.2 + math.sin(t * 0.6), 7)
		nodeLookAt(world.camera, 0, 1.2, -5)
		sceneSetBloom(0.6, 0.6 + 0.4 * K.decay("kicks", t, 7))
	end,
}


-- The turntable:  the record turns at its speed and is scratched back and forth on every snare, the
-- tonearm creeps inward, and the camera cuts round it every two beats.
local TURNTABLE_SHOTS = {
	{ -7, 2.2, 6, 0, 0, 0 }, { 0, 9, 0.1, 0, 0, 0 }, { 6.5, 1.4, 3.5, 2.5, 0.2, 1.5 }, { -1.5, 0.7, 6, 0, 0.1, 0 },
}

local TURNTABLE = {
	enter = function(t)
		hideAll()
		nodeSetVisible(world.vinyl, true)
		sceneSetSkyIntensity(0.6)
		lightSetIntensity(world.sun, 2)
		world.recordLast = t
	end,
	draw = function(t, bar, k)
		local age     = K.hitAge("snares", t)
		local scratch = -45 * math.sin(age * 2 * math.pi * 3) * math.exp(-age * 7)
		local shot    = TURNTABLE_SHOTS[math.floor(K.beat(t) / 2) % #TURNTABLE_SHOTS + 1]
		local drift   = math.sin(t * 0.7) * 0.4

		world.recordAngle = (world.recordAngle or 0) + (t - world.recordLast) * RECORD_RPM * 6
		world.recordLast  = t
		nodeSetRotation(world.record, 0, -(world.recordAngle + scratch), 0)
		nodeSetRotation(world.tonearm, 0, -21 - 6 * k, 0)
		nodeSetPosition(world.camera, shot[1] + drift, shot[2], shot[3])
		nodeLookAt(world.camera, shot[4], shot[5], shot[6])
		spots(t, 0.8)
		K.strobe(t, "kicks", 16, 255, 255, 255, 25)
	end,
}


-- The party:  the club with everything on.  The final version turns the camera faster and the lasers
-- change twice a bar.
local function party(final)
	return {
		enter = function(t)
			hideAll()
			showClub(true)
			nodeSetVisible(world.laserFan, true)
		end,
		draw = function(t, bar, k)
			if final then
				orbit(t, 9 + 3 * math.sin(t * 0.5), 2 + 2 * math.sin(t * 0.3), 0.45, BALL_Y - 1)
			else
				orbit(t, 13, 3.5, 0.18, BALL_Y - 1.5)
			end
			ballSpin(t, BALL_Y, final and 70 or 40, 1)
			spots(t, 1)
			lasers(t, 1, final and 2 or 1)
			floor(t, math.floor((bar - 97) / 2) % 4, 1)
			sceneSetBloom(0.7, 0.55 + (final and 0.4 or 0.2) * K.decay("kicks", t, 7))
			K.bobs(t, bar, art.bob, 36, 0.9, 13, W / 2, 150)
			K.strobe(t, "kicks", 18, 255, 255, 255, final and 50 or 25)
		end,
	}
end


-- The scenes -------------------------------------------------------------------------------------------

local SCENES = {
	-- Bars 1 to 8:  the choppy intro.  Copper bars light only while the band plays, so the gaps in
	-- the groove are black;  the title drops in a letter every two beats.
	{
		from = 0, to = 9,
		enter = function(t)
			hideAll()
		end,
		draw = function(t, bar, k)
			K.fill(0, 0, 0)
			local gate = K.clamp((K.env("level", t) - 0.15) * 2.5, 0, 1)

			copperBars(t, 10, 210, 170, t * 0.05, math.floor(255 * gate))
			titleDrop(t, K.beat(K.barTime(2)), 2, 230)
			if bar >= 7 then
				local w = K.width(art.singe) * 0.5

				spriteSetAlpha(art.singe, math.floor(255 * K.smooth(7, 7.5, bar)))
				K.draw(art.singe, W / 2 - w / 2, 330, W / 2 + w / 2, 330 + K.height(art.singe) / 2)
				spriteSetAlpha(art.singe, 255)
				K.text(W / 2, 312, "PRESENTED WITH", 18, 200, 180, 140, "center")
			end
			K.strobe(t, "kicks", 16, 255, 220, 160, 40)
			if bar > 8.75 then
				K.flash(255, 255, 255, math.floor(255 * K.smooth(8.75, 9, bar)))
			end
		end,
	},
	-- Bars 9 to 16:  the club.  The ball comes down over the floor, the spots sweep, the floor
	-- checker swaps on every beat, and the title settles at the bottom.
	{
		from = 9, to = 17,
		enter = function(t)
			hideAll()
			showClub(true)
		end,
		draw = function(t, bar, k)
			local drop = K.easeOut((bar - 9) / 2)

			ballSpin(t, K.lerp(16, BALL_Y, drop), 30, drop)
			orbit(t, 13 - 3 * k, 2.5 + 2 * k, 0.12, 3.5 + 1.5 * drop)
			spots(t, drop)
			floor(t, 0, 0.3 + 0.7 * drop)
			if bar >= 13 then
				local a = math.floor(255 * K.smooth(13, 13.5, bar))
				local w = K.width(art.logo) * 0.85
				local h = K.height(art.logo) * 0.85

				spriteSetAlpha(art.logo, a)
				K.draw(art.logo, W / 2 - w / 2, H - 20 - h, W / 2 + w / 2, H - 20)
				spriteSetAlpha(art.logo, 255)
			end
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(9, 9.25, bar))))
		end,
	},
	-- Bars 17 to 24:  the lead comes in, and the rotozoomer with it:  the floor's own disco tile, on a
	-- screen that turns and zooms, under copper bars coloured by the note being played and the
	-- scroller.
	{
		from = 17, to = 25,
		enter = function(t)
			hideAll()
			nodeSetVisible(world.roto, true)
		end,
		draw = function(t, bar, k)
			nodeSetPosition(world.camera, 0, 0, 0)
			nodeLookAt(world.camera, 0, 0, -1)
			local zoom = 4 + 3 * math.sin(t * 0.6) + 2 * K.decay("kicks", t, 7)

			materialSetTiling(world.rotoMaterial, zoom * W / H, zoom)
			nodeSetRotation(world.roto, 0, 0, t * 30 + math.sin(t * 0.8) * 40)
			local note, clear = K.note(t)

			copperBars(t, 6, 40, 30, note / 12, math.floor(120 + 135 * clear))
			K.scroller(t, art.font, SCROLL_TEXT, H - 80, 22, K.barTime(17), K.barTime(25))
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(17, 17.2, bar))))
		end,
	},
	-- Bars 25 to 28:  a kaleidoscope of the plasma, four mirrored copies, under vector bobs that take
	-- a new shape every two bars.  Then the dot cloud.
	{
		from = 25, to = 29,
		enter = function(t)
			hideAll()
			nodeSetVisible(world.kaleido, true)
		end,
		draw = function(t, bar, k)
			K.plasmaUpdate(art.plasma, t)
			for _, m in ipairs(world.kaleidoMaterials) do
				materialSetTexture(m, art.plasma.sprite)
			end
			nodeSetPosition(world.camera, 0, 0, 0)
			nodeLookAt(world.camera, 0, 0, -1)
			nodeSetRotation(world.kaleido, 0, 0, math.sin(t * 0.4) * 20)
			nodeSetScale(world.kaleido, 1.15 + 0.1 * K.decay("kicks", t, 6))
			K.bobs(t, bar, art.bob, 56, 1.4, 21, W / 2, H / 2)
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(25, 25.2, bar))))
		end,
	},
	at(29, 33, DOT_CLOUD),
	-- Bars 33 to 40:  the chop comes back, and the picture cuts on every beat between the club's
	-- corners;  the gaps in the groove go black.
	{
		from = 33, to = 41,
		enter = function(t)
			hideAll()
			showClub(true)
			nodeSetVisible(world.laserFan, true)
		end,
		draw = function(t, bar, k)
			local beat = math.floor(K.beat(t))
			local shots = {
				{ 0, 1.5, 10, 0, 5, 0 }, { 9, 9, 9, 0, 3, 0 }, { 0, 13, 0.1, 0, 0, 0 }, { -3, 6.5, 3, 0, 6.2, 0 },
				{ 12, 1, -4, 0, 4, 0 }, { 0, 4, -11, 0, 5, 0 }, { -9, 2, 6, 0, 6, 0 }, { 3, 5.5, 2.5, 0, 6.2, 0 },
			}
			local s = shots[beat % #shots + 1]

			nodeSetPosition(world.camera, s[1], s[2], s[3])
			nodeLookAt(world.camera, s[4], s[5], s[6])
			ballSpin(t, BALL_Y, 40, 1)
			spots(t, 1)
			lasers(t, 0.8)
			floor(t, 3, 1)
			local gate = K.clamp((K.env("level", t) - 0.12) * 3, 0, 1)

			K.flash(0, 0, 0, math.floor(255 * (1 - gate)))
			K.flash(255, 255, 255, math.floor(160 * math.exp(-(K.beat(t) % 1) * 14)))
		end,
	},
	-- Bars 41 to 48:  the twister over copper bars, drawn one scanline at a time.
	{
		from = 41, to = 49,
		enter = function(t)
			hideAll()
		end,
		draw = function(t, bar, k)
			K.fill(14, 4, 22)
			copperBars(t, 14, 220, 200, t * 0.03, 200)
			twister(t, W / 2 + math.sin(t * 0.7) * 120)
			K.scroller(t, art.font, SECOND_TEXT, 30, 14, K.barTime(41), K.barTime(49))
			K.strobe(t, "kicks", 14, 255, 255, 255, 50)
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(41, 41.2, bar))))
		end,
	},
	-- Bars 49 to 52:  the boing ball, bouncing on every beat and crossing the room every bar, while
	-- a ball drops from the ceiling on every snare and piles up on the floor.  Then the equalizer.
	{
		from = 49, to = 53,
		enter = function(t)
			hideAll()
			showClub(false)
			nodeSetVisible(world.boing, true)
			lightSetIntensity(world.sun, 3)
		end,
		draw = function(t, bar, k)
			local b      = K.beat(t)
			local hop    = b % 1
			local across = math.sin((bar - 49) * math.pi)

			nodeSetPosition(world.boing, across * 8, 1.6 + 4 * 4 * hop * (1 - hop) * 1.4, 2)
			nodeSetRotation(world.boing, 20, t * 120, 0)
			orbit(t, 12, 4, 0.08, 2.5, 1.2)
			floor(t, 1, 0.8)
			spots(t, 0.6)
			if K.hitCount("snares", lastT, t) > 0 and #world.rain < RAIN_MAX then
				local n = nodeNew()

				nodeSetMesh(n, world.rainMesh, world.rainMaterials[#world.rain % #world.rainMaterials + 1])
				nodeSetPosition(n, (math.random() - 0.5) * 16, 14, (math.random() - 0.5) * 10 - 2)
				bodyNew(n, BODY_DYNAMIC, SHAPE_SPHERE, 0.32)
				bodySetMass(n, 0.5)
				bodySetBounce(n, 0.7)
				world.rain[#world.rain + 1] = n
			end
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(49, 49.2, bar))))
		end,
		leave = function(t)
			for _, n in ipairs(world.rain) do
				bodyDelete(n)
				nodeDelete(n)
			end
			world.rain = {}
		end,
	},
	at(53, 57, EQUALIZER),
	-- Bars 57 to 60:  glenz glass in the tunnel, the tunnel scrubbed by the kick.  Then the turntable.
	{
		from = 57, to = 61,
		enter = function(t)
			hideAll()
			nodeSetVisible(world.tunnel, true)
			nodeSetVisible(world.glenz, true)
			world.tunnelPhase = 0
			world.tunnelLast  = t
			sceneSetSkyIntensity(1.5)
			lightSetIntensity(world.sun, 5)
		end,
		draw = function(t, bar, k)
			nodeSetPosition(world.camera, 0, 0, 0)
			nodeLookAt(world.camera, 0, 0, -1)
			world.tunnelPhase = world.tunnelPhase + (t - world.tunnelLast) * (0.5 + 1.5 * K.decay("kicks", t, 5))
			world.tunnelLast  = t
			K.tunnelUpdate(art.tunnel, (world.tunnelPhase / TUNNEL_LAP) % 1, 0)
			materialSetTexture(world.tunnelMaterial, art.tunnel.sprite)
			nodeSetRotation(world.tunnel, 0, 0, -t * 20)
			local pump = 1 + 0.2 * K.decay("kicks", t, 8)

			nodeSetPosition(world.glenz, 0, 0, -6)
			nodeSetScale(world.glenz, pump)
			nodeSetRotation(world.glenzOuter, t * 37, t * 53, t * 19)
			nodeSetRotation(world.glenzInner, -t * 61, t * 29, -t * 43)
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(57, 57.2, bar))))
		end,
	},
	at(61, 65, TURNTABLE),
	-- Bars 65 to 72:  the laser show, in a haze, the camera moving through the beams.
	{
		from = 65, to = 73,
		enter = function(t)
			hideAll()
			showClub(true)
			nodeSetVisible(world.laserFan, true)
			sceneSetFog(16, 8, 30, 6, 70)
		end,
		draw = function(t, bar, k)
			orbit(t, 12, 2 + math.sin(t * 0.4) * 1.5, -0.15, 5)
			ballSpin(t, BALL_Y, 45, 1)
			spots(t, 0.8)
			lasers(t, 1, 2)
			floor(t, 2, 0.7)
			K.strobe(t, "snares", 20, 255, 255, 255, 60)
		end,
	},
	-- Bars 73 to 80:  the plasma flat on the screen, the Singe logo rotozoomed over it, a ring of bobs.
	{
		from = 73, to = 81,
		enter = function(t)
			hideAll()
		end,
		draw = function(t, bar, k)
			K.plasmaUpdate(art.plasma, t)
			K.under(art.plasma.sprite, 0, 0, W, H, nil, nil, nil, nil, true)
			local punch = 1 + 0.3 * K.decay("kicks", t, 8)

			for i = 1, 12 do
				local a = i / 12 * 2 * math.pi + t
				local r = 190 * punch
				local cr, cg, cb = K.hue(i / 12 + t * 0.1)

				spriteSetTint(art.bob, cr, cg, cb)
				K.draw(art.bob, W / 2 + math.cos(a) * r - 18, H / 2 + math.sin(a) * r * 0.8 - 18, W / 2 + math.cos(a) * r + 18, H / 2 + math.sin(a) * r * 0.8 + 18)
			end
			spriteSetTint(art.bob, 255, 255, 255)
			K.turn(art.singe, W / 2, H / 2, math.sin(t * 0.9) * 35, (1 + 0.4 * math.sin(t * 1.1)) * punch)
			K.flash(255, 255, 255, math.floor(255 * (1 - K.smooth(73, 73.2, bar))))
		end,
	},
	-- Bars 81 to 88:  the breakdown.  The kick is gone;  the club is dark but for the ball and its
	-- sparkles, turning slowly.  When the bass returns at bar 85 the floor comes back a tile a beat.
	{
		from = 81, to = 89,
		enter = function(t)
			hideAll()
			showClub(true)
		end,
		draw = function(t, bar, k)
			orbit(t, 9, 3 + k * 2, 0.06, BALL_Y)
			ballSpin(t, BALL_Y, 12, 0.8 + 0.4 * k)
			sceneSetSkyIntensity(0.4 + 0.6 * k)
			local lit = (bar >= 85) and math.floor(K.beat(t) - K.beat(K.barTime(85))) * 9 or 0

			for n, tile in ipairs(world.tiles) do
				local on = ((n * 37) % #world.tiles) < lit
				local c  = DISCO[n % #DISCO + 1]
				local v  = on and 0.8 or 0

				materialSetEmissive(tile.material, math.floor(c[1] * v), math.floor(c[2] * v), math.floor(c[3] * v))
			end
		end,
	},
	-- Bars 89 to 96:  the build.  Everything comes back on, the camera climbs, and the beat strobes.
	{
		from = 89, to = 97,
		enter = function(t)
			hideAll()
			showClub(true)
			nodeSetVisible(world.laserFan, true)
		end,
		draw = function(t, bar, k)
			orbit(t, 14 - 4 * k, 2 + 7 * k, 0.2, BALL_Y - 2 * k)
			ballSpin(t, BALL_Y, 30 + 30 * k, 1)
			spots(t, k)
			lasers(t, k)
			floor(t, math.floor((bar - 89) / 2) % 4, 0.4 + 0.6 * k)
			K.flash(255, 255, 255, math.floor(110 * k * math.exp(-(K.beat(t) % 1) * 10)))
			copperBars(t, 4, 10, 8, t * 0.1, math.floor(200 * k))
			copperBars(t, 4, H - 40, 8, t * 0.1 + 0.5, math.floor(200 * k))
		end,
	},
	-- Bars 97 to 112:  the party, cutting faster as it goes:  the club, the dot cloud, the equalizer,
	-- the club with the camera spinning, the turntable, and the club again to the last downbeat.
	at(97, 101, party(false)),
	at(101, 103, DOT_CLOUD),
	at(103, 105, EQUALIZER),
	at(105, 107, party(true)),
	at(107, 109, TURNTABLE),
	at(109, 113, party(true)),
	-- Over the whole party, whatever is cut to:  the scroller, and the flash into the last downbeat.
	{
		from = 97, to = 113,
		draw = function(t, bar, k)
			K.scroller(t, art.font, PARTY_TEXT, H - 70, 16, K.barTime(97), K.barTime(113))
			if bar > 112.5 then
				K.flash(255, 255, 255, math.floor(200 * K.smooth(112.5, 113, bar)))
			end
		end,
	},
	-- Bar 113 on:  the last downbeat.  The ball shatters, its facets rain onto the floor, and the
	-- lights go down.
	{
		from = 113, to = 200,
		enter = function(t)
			hideAll()
			showClub(true)
			world.lastSpin  = 70
			world.lastBallY = BALL_Y
			shatter(t)
			world.endCamera = t
		end,
		draw = function(t, bar, k)
			local p = t - K.barTime(113)

			orbit(world.endCamera + p * 0.3, 13 + p * 0.5, 3 + p * 0.25, 0.2, 2)
			lightSetIntensity(world.ballSpot, 0)
			sceneSetSkyIntensity(math.max(0.25, 1 - p * 0.12))
			floor(t, 1, math.max(0, 1 - p * 0.15))
			for i, l in ipairs(world.spots) do
				lightSetIntensity(l, math.max(0, 120 - p * 25))
			end
			K.flash(255, 255, 255, math.floor(255 * math.exp(-p * 3)))
		end,
	},
	-- The time at the end of each frame, for "what happened since last frame".
	{
		from = -10, to = 1000,
		draw = function(t, bar, k)
			lastT = t
		end,
	},
}

loadArt()
buildWorld()
hideAll()
K.run(SCENES)