Activity 2.11: Sound and Polish

The Idea

Your game works and it feels like nothing. Shots leave silently, enemies vanish without complaint, and losing a life looks the same as not losing one until you count the icons.

Feedback is not decoration. It is how the game confirms that what you did registered, and it is the difference between a program that responds and a program that merely changes. This activity adds three sounds and one shaking screen, and it is the shortest distance between what you have and something that feels like a game.

Loading a sound

Download all three and put them in your skynest folder, next to main.lua and ship.png.

shoot.wav — 0.18s hit.wav — 0.12s explode.wav — 0.55s

sounds = {
  shoot = love.audio.newSource("shoot.wav", "static"),
  hit = love.audio.newSource("hit.wav", "static"),
  explode = love.audio.newSource("explode.wav", "static"),
}

The second argument is required, and it is a real decision. "static" decodes the whole file into memory at load, which is right for short effects you will play hundreds of times. "stream" decodes as it plays, which is right for a three-minute music track you would rather not unpack into RAM.

A table keyed by name beats three separate locals, and it is the record table from Activity 1.10 doing ordinary work. Loading goes in love.load for the third time on this course, for the third identical reason.

The thing about play() that will confuse you

Here is the behavior nobody warns you about, taken from LÖVE's own source rather than from folklore: calling play() on a Source that is already playing does nothing at all. It does not restart the sound and it does not layer a second copy over it. The call is simply lost, and nothing tells you.

That matters immediately, because your fire cooldown is 0.15 seconds and shoot.wav is 0.18 seconds long. Hold the fire button for five seconds and you fire thirty shots and hear fifteen of them. I ran exactly that under a harness: 15 heard, 15 silently discarded. The game is not broken, the gun just sounds wrong and you cannot see why.

-- Fires thirty times. Fifteen of them make no sound at all.
sounds.shoot:play()

-- Fires thirty times. Thirty of them are heard.
sounds.shoot:clone():play()

clone() hands back a new Source pointing at the same decoded audio — LÖVE's copy constructor shares the buffer and copies the pitch, volume and loop settings — so cloning a "static" sound is cheap. Same five seconds, same thirty shots, thirty heard. Note that cloning a "stream" source is not cheap, because it has to clone the decoder too.

There is a second reason to clone, and it is the more interesting one. Pitch and volume belong to the Source, not to the sound. If you want every hit slightly detuned so a burst of them does not sound mechanical, each hit needs a Source of its own.

local thud = sounds.hit:clone()
thud:setPitch(0.9 + math.random() * 0.3)
thud:play()

There is a ceiling. LÖVE keeps a pool of 64 simultaneous voices; past that, play() returns false and the sound is dropped. Thirty shots over five seconds is nowhere near it, and a clone every frame would be. Since play() returns a boolean, you can find out rather than wonder.

Not everything should clone

The explode sound stays a single shared Source on purpose. You can only lose one life at a time, and if two losses ever did coincide, one explosion is what you would want to hear. Deciding which sounds clone is a design question, not a mechanical one, and "clone everything" is the wrong answer as reliably as "clone nothing".

Volume is the same kind of judgment. Shooting happens constantly and belongs underneath everything else, so it is set to 0.35 once at load and every clone inherits it.

Screen shake, and the transform stack

love.graphics.push()
love.graphics.translate(math.random(-6, 6), math.random(-6, 6))

-- everything drawn here is offset

love.graphics.pop()

-- and everything drawn here is not

translate moves the coordinate system rather than any object, which is why one call shakes the entire world and none of your drawing code has to know about it. push saves the current transform and pop restores it, so the offset applies to exactly what you put between them.

The HUD goes after the pop. A score that jitters is a bug, not an effect, and the world-versus-screen split from Activity 2.9 is finally the difference between two lines of code rather than a distinction on paper.

One place the countdown cannot go

The shake timer is the same accumulator you have written four times. It is also the first one that cannot live with the others.

function love.update(dt)
  shake = shake - dt

  if gameState ~= "playing" then
    return
  end

  -- the rest of the timers live down here
end

The reason is the guard from Activity 2.10. The last shake of a run starts on the hit that ends the run, and one frame later update returns early forever — so a countdown below the guard never runs again, and the screen shakes behind the game-over text until you quit.

I measured both versions over the same ten-second run. Above the guard: 75 shaking frames, three neat bursts. Below it: 184, still going when the run ended. The guard is a decision about which work belongs to a run, not a gate on all work, and this is the first time the difference bites.

Build

The three .wav files go beside main.lua. enemy.lua and collision.lua are untouched.

Task 1: Three sounds

Add a sounds local to the top group of the state block — it belongs to the program, not to a run — and fill it in love.load.
Turn the shooting down to 0.35 and the hit to 0.6. The loudest sound in a game is rarely the one that happens most.
Play shoot when a bullet is created, hit when a bullet lands, and explode when a life is lost.
Hold the fire button and listen. The gun stutters, because half the shots are landing on a Source that is still busy. Nothing is broken; you are hearing exactly what the code asked for.

1
-- main.lua
2

3
local Enemy = require("enemy")
4
local collision = require("collision")
5

6
local ship
7
local font
8
local titleFont
9
local sounds
10
local spawnEvery = 0.8
11
local gameState = "menu"
12

13
local player
14
local bullets
15
local fireCooldown
16
local enemies
17
local spawnTimer
18
local score
19
local lives
20
local invuln
21

22
local function resetGame()
23
  player = { x = 400, y = 500, size = 40, speed = 300 }
24
  bullets = {}
25
  fireCooldown = 0
26
  enemies = {}
27
  spawnTimer = 0
28
  score = 0
29
  lives = 3
30
  invuln = 0
31
end
32

33
function love.load()
34
  love.graphics.setBackgroundColor(0.05, 0.05, 0.1)
35
  math.randomseed(os.time())
36
  ship = love.graphics.newImage("ship.png")
37
  font = love.graphics.newFont(20)
38
  titleFont = love.graphics.newFont(48)
39
  love.graphics.setFont(font)
40

41
  sounds = {
42
    shoot = love.audio.newSource("shoot.wav", "static"),
43
    hit = love.audio.newSource("hit.wav", "static"),
44
    explode = love.audio.newSource("explode.wav", "static"),
45
  }
46
  sounds.shoot:setVolume(0.35)
47
  sounds.hit:setVolume(0.6)
48

49
  resetGame()
50
end
51

52
function love.keypressed(key)
53
  if key == "escape" then
54
    love.event.quit()
55
  elseif key == "space" and gameState ~= "playing" then
56
    resetGame()
57
    gameState = "playing"
58
  end
59
end
60

61
function love.update(dt)
62
  if gameState ~= "playing" then
63
    return
64
  end
65

66
  if love.keyboard.isDown("left", "a") then
67
    player.x = player.x - player.speed * dt
68
  end
69
  if love.keyboard.isDown("right", "d") then
70
    player.x = player.x + player.speed * dt
71
  end
72

73
  local half = player.size / 2
74
  player.x = math.max(half, math.min(love.graphics.getWidth() - half, player.x))
75

76
  fireCooldown = fireCooldown - dt
77
  invuln = invuln - dt
78

79
  if love.keyboard.isDown("space") and fireCooldown <= 0 then
80
    table.insert(bullets, { x = player.x, y = player.y - 30, size = 6, speed = 500 })
81
    fireCooldown = 0.15
82
    sounds.shoot:play()
83
  end
84

85
  for i = #bullets, 1, -1 do
86
    local b = bullets[i]
87
    b.y = b.y - b.speed * dt
88
    if b.y < -20 then
89
      table.remove(bullets, i)
90
    end
91
  end
92

93
  spawnTimer = spawnTimer - dt
94
  if spawnTimer <= 0 then
95
    table.insert(enemies, Enemy.new(math.random(40, love.graphics.getWidth() - 40)))
96
    spawnTimer = spawnEvery
97
  end
98

99
  for i = #enemies, 1, -1 do
100
    local e = enemies[i]
101
    e:update(dt)
102
    if e.y > love.graphics.getHeight() + 20 then
103
      table.remove(enemies, i)
104
    end
105
  end
106

107
  if invuln <= 0 then
108
    for i = #enemies, 1, -1 do
109
      if collision.overlaps(enemies[i], player) then
110
        table.remove(enemies, i)
111
        lives = lives - 1
112
        invuln = 2
113
        sounds.explode:play()
114
        if lives <= 0 then
115
          gameState = "gameover"
116
        end
117
        break
118
      end
119
    end
120
  end
121

122
  for i = #enemies, 1, -1 do
123
    for j = #bullets, 1, -1 do
124
      if collision.overlaps(enemies[i], bullets[j]) then
125
        table.remove(bullets, j)
126
        sounds.hit:play()
127
        enemies[i].hp = enemies[i].hp - 1
128
        if enemies[i].hp <= 0 then
129
          table.remove(enemies, i)
130
          score = score + 1
131
        end
132
        break
133
      end
134
    end
135
  end
136
end
137

138
local function drawHud()
139
  love.graphics.setColor(1, 1, 1)
140
  love.graphics.print("Score: " .. score, 10, 12)
141

142
  for i = 1, lives do
143
    local x = love.graphics.getWidth() - 24 - (i - 1) * 30
144
    love.graphics.draw(ship, x, 24, 0, 1, 1, ship:getWidth() / 2, ship:getHeight() / 2)
145
  end
146
end
147

148
local function drawOverlay(title, subtitle)
149
  love.graphics.setColor(0, 0, 0, 0.7)
150
  love.graphics.rectangle("fill", 0, 0, love.graphics.getWidth(), love.graphics.getHeight())
151

152
  love.graphics.setColor(1, 1, 1)
153
  love.graphics.setFont(titleFont)
154
  love.graphics.printf(title, 0, 220, love.graphics.getWidth(), "center")
155

156
  love.graphics.setFont(font)
157
  love.graphics.printf(subtitle, 0, 300, love.graphics.getWidth(), "center")
158
end
159

160
function love.draw()
161
  local blink = invuln > 0 and math.floor(invuln * 10) % 2 == 1
162

163
  if not blink then
164
    love.graphics.setColor(1, 1, 1)
165
    love.graphics.draw(ship, player.x, player.y, 0, 2, 2, ship:getWidth() / 2, ship:getHeight() / 2)
166
  end
167

168
  love.graphics.setColor(1, 0.9, 0.3)
169
  for _, b in ipairs(bullets) do
170
    love.graphics.rectangle("fill", b.x - 2, b.y - 8, 4, 16)
171
  end
172

173
  for _, e in ipairs(enemies) do
174
    e:draw()
175
  end
176

177
  drawHud()
178

179
  if gameState == "menu" then
180
    drawOverlay("SKYNEST", "Press space to play")
181
  elseif gameState == "gameover" then
182
    drawOverlay("GAME OVER", "Score " .. score .. " - press space to play again")
183
  end
184
end

Task 2: Clone the ones that overlap

Shooting becomes sounds.shoot:clone():play(). One character of thought, and the stutter is gone.
Give the hit sound its own clone and a random pitch between 0.9 and 1.2, so a run of hits does not sound like a machine.
Leave explode alone. One shared Source is correct there, and being able to say why is the point of the task.
Hold fire again. Every shot now speaks, and the two sounds sit on top of each other the way they should.

1
-- main.lua
2

3
local Enemy = require("enemy")
4
local collision = require("collision")
5

6
local ship
7
local font
8
local titleFont
9
local sounds
10
local spawnEvery = 0.8
11
local gameState = "menu"
12

13
local player
14
local bullets
15
local fireCooldown
16
local enemies
17
local spawnTimer
18
local score
19
local lives
20
local invuln
21

22
local function resetGame()
23
  player = { x = 400, y = 500, size = 40, speed = 300 }
24
  bullets = {}
25
  fireCooldown = 0
26
  enemies = {}
27
  spawnTimer = 0
28
  score = 0
29
  lives = 3
30
  invuln = 0
31
end
32

33
function love.load()
34
  love.graphics.setBackgroundColor(0.05, 0.05, 0.1)
35
  math.randomseed(os.time())
36
  ship = love.graphics.newImage("ship.png")
37
  font = love.graphics.newFont(20)
38
  titleFont = love.graphics.newFont(48)
39
  love.graphics.setFont(font)
40

41
  sounds = {
42
    shoot = love.audio.newSource("shoot.wav", "static"),
43
    hit = love.audio.newSource("hit.wav", "static"),
44
    explode = love.audio.newSource("explode.wav", "static"),
45
  }
46
  sounds.shoot:setVolume(0.35)
47
  sounds.hit:setVolume(0.6)
48

49
  resetGame()
50
end
51

52
function love.keypressed(key)
53
  if key == "escape" then
54
    love.event.quit()
55
  elseif key == "space" and gameState ~= "playing" then
56
    resetGame()
57
    gameState = "playing"
58
  end
59
end
60

61
function love.update(dt)
62
  if gameState ~= "playing" then
63
    return
64
  end
65

66
  if love.keyboard.isDown("left", "a") then
67
    player.x = player.x - player.speed * dt
68
  end
69
  if love.keyboard.isDown("right", "d") then
70
    player.x = player.x + player.speed * dt
71
  end
72

73
  local half = player.size / 2
74
  player.x = math.max(half, math.min(love.graphics.getWidth() - half, player.x))
75

76
  fireCooldown = fireCooldown - dt
77
  invuln = invuln - dt
78

79
  if love.keyboard.isDown("space") and fireCooldown <= 0 then
80
    table.insert(bullets, { x = player.x, y = player.y - 30, size = 6, speed = 500 })
81
    fireCooldown = 0.15
82
    sounds.shoot:clone():play()
83
  end
84

85
  for i = #bullets, 1, -1 do
86
    local b = bullets[i]
87
    b.y = b.y - b.speed * dt
88
    if b.y < -20 then
89
      table.remove(bullets, i)
90
    end
91
  end
92

93
  spawnTimer = spawnTimer - dt
94
  if spawnTimer <= 0 then
95
    table.insert(enemies, Enemy.new(math.random(40, love.graphics.getWidth() - 40)))
96
    spawnTimer = spawnEvery
97
  end
98

99
  for i = #enemies, 1, -1 do
100
    local e = enemies[i]
101
    e:update(dt)
102
    if e.y > love.graphics.getHeight() + 20 then
103
      table.remove(enemies, i)
104
    end
105
  end
106

107
  if invuln <= 0 then
108
    for i = #enemies, 1, -1 do
109
      if collision.overlaps(enemies[i], player) then
110
        table.remove(enemies, i)
111
        lives = lives - 1
112
        invuln = 2
113
        sounds.explode:play()
114
        if lives <= 0 then
115
          gameState = "gameover"
116
        end
117
        break
118
      end
119
    end
120
  end
121

122
  for i = #enemies, 1, -1 do
123
    for j = #bullets, 1, -1 do
124
      if collision.overlaps(enemies[i], bullets[j]) then
125
        table.remove(bullets, j)
126

127
        local thud = sounds.hit:clone()
128
        thud:setPitch(0.9 + math.random() * 0.3)
129
        thud:play()
130

131
        enemies[i].hp = enemies[i].hp - 1
132
        if enemies[i].hp <= 0 then
133
          table.remove(enemies, i)
134
          score = score + 1
135
        end
136
        break
137
      end
138
    end
139
  end
140
end
141

142
local function drawHud()
143
  love.graphics.setColor(1, 1, 1)
144
  love.graphics.print("Score: " .. score, 10, 12)
145

146
  for i = 1, lives do
147
    local x = love.graphics.getWidth() - 24 - (i - 1) * 30
148
    love.graphics.draw(ship, x, 24, 0, 1, 1, ship:getWidth() / 2, ship:getHeight() / 2)
149
  end
150
end
151

152
local function drawOverlay(title, subtitle)
153
  love.graphics.setColor(0, 0, 0, 0.7)
154
  love.graphics.rectangle("fill", 0, 0, love.graphics.getWidth(), love.graphics.getHeight())
155

156
  love.graphics.setColor(1, 1, 1)
157
  love.graphics.setFont(titleFont)
158
  love.graphics.printf(title, 0, 220, love.graphics.getWidth(), "center")
159

160
  love.graphics.setFont(font)
161
  love.graphics.printf(subtitle, 0, 300, love.graphics.getWidth(), "center")
162
end
163

164
function love.draw()
165
  local blink = invuln > 0 and math.floor(invuln * 10) % 2 == 1
166

167
  if not blink then
168
    love.graphics.setColor(1, 1, 1)
169
    love.graphics.draw(ship, player.x, player.y, 0, 2, 2, ship:getWidth() / 2, ship:getHeight() / 2)
170
  end
171

172
  love.graphics.setColor(1, 0.9, 0.3)
173
  for _, b in ipairs(bullets) do
174
    love.graphics.rectangle("fill", b.x - 2, b.y - 8, 4, 16)
175
  end
176

177
  for _, e in ipairs(enemies) do
178
    e:draw()
179
  end
180

181
  drawHud()
182

183
  if gameState == "menu" then
184
    drawOverlay("SKYNEST", "Press space to play")
185
  elseif gameState == "gameover" then
186
    drawOverlay("GAME OVER", "Score " .. score .. " - press space to play again")
187
  end
188
end

Task 3: Make the screen flinch

Add shake to the per-run group and zero it in resetGame. Set it to 0.4 when a life is lost.
Count it down above the early return, on its own, for the reason above.
Wrap the world in push and pop and translate by a small random offset while the timer runs. Leave the HUD and the overlay outside.
Die on purpose. The world lurches for four tenths of a second, the score sits perfectly still, and then it stops.

1
-- main.lua
2

3
local Enemy = require("enemy")
4
local collision = require("collision")
5

6
local ship
7
local font
8
local titleFont
9
local sounds
10
local spawnEvery = 0.8
11
local gameState = "menu"
12

13
local player
14
local bullets
15
local fireCooldown
16
local enemies
17
local spawnTimer
18
local score
19
local lives
20
local invuln
21
local shake
22

23
local function resetGame()
24
  player = { x = 400, y = 500, size = 40, speed = 300 }
25
  bullets = {}
26
  fireCooldown = 0
27
  enemies = {}
28
  spawnTimer = 0
29
  score = 0
30
  lives = 3
31
  invuln = 0
32
  shake = 0
33
end
34

35
function love.load()
36
  love.graphics.setBackgroundColor(0.05, 0.05, 0.1)
37
  math.randomseed(os.time())
38
  ship = love.graphics.newImage("ship.png")
39
  font = love.graphics.newFont(20)
40
  titleFont = love.graphics.newFont(48)
41
  love.graphics.setFont(font)
42

43
  sounds = {
44
    shoot = love.audio.newSource("shoot.wav", "static"),
45
    hit = love.audio.newSource("hit.wav", "static"),
46
    explode = love.audio.newSource("explode.wav", "static"),
47
  }
48
  sounds.shoot:setVolume(0.35)
49
  sounds.hit:setVolume(0.6)
50

51
  resetGame()
52
end
53

54
function love.keypressed(key)
55
  if key == "escape" then
56
    love.event.quit()
57
  elseif key == "space" and gameState ~= "playing" then
58
    resetGame()
59
    gameState = "playing"
60
  end
61
end
62

63
function love.update(dt)
64
  shake = shake - dt
65

66
  if gameState ~= "playing" then
67
    return
68
  end
69

70
  if love.keyboard.isDown("left", "a") then
71
    player.x = player.x - player.speed * dt
72
  end
73
  if love.keyboard.isDown("right", "d") then
74
    player.x = player.x + player.speed * dt
75
  end
76

77
  local half = player.size / 2
78
  player.x = math.max(half, math.min(love.graphics.getWidth() - half, player.x))
79

80
  fireCooldown = fireCooldown - dt
81
  invuln = invuln - dt
82

83
  if love.keyboard.isDown("space") and fireCooldown <= 0 then
84
    table.insert(bullets, { x = player.x, y = player.y - 30, size = 6, speed = 500 })
85
    fireCooldown = 0.15
86
    sounds.shoot:clone():play()
87
  end
88

89
  for i = #bullets, 1, -1 do
90
    local b = bullets[i]
91
    b.y = b.y - b.speed * dt
92
    if b.y < -20 then
93
      table.remove(bullets, i)
94
    end
95
  end
96

97
  spawnTimer = spawnTimer - dt
98
  if spawnTimer <= 0 then
99
    table.insert(enemies, Enemy.new(math.random(40, love.graphics.getWidth() - 40)))
100
    spawnTimer = spawnEvery
101
  end
102

103
  for i = #enemies, 1, -1 do
104
    local e = enemies[i]
105
    e:update(dt)
106
    if e.y > love.graphics.getHeight() + 20 then
107
      table.remove(enemies, i)
108
    end
109
  end
110

111
  if invuln <= 0 then
112
    for i = #enemies, 1, -1 do
113
      if collision.overlaps(enemies[i], player) then
114
        table.remove(enemies, i)
115
        lives = lives - 1
116
        invuln = 2
117
        shake = 0.4
118
        sounds.explode:play()
119
        if lives <= 0 then
120
          gameState = "gameover"
121
        end
122
        break
123
      end
124
    end
125
  end
126

127
  for i = #enemies, 1, -1 do
128
    for j = #bullets, 1, -1 do
129
      if collision.overlaps(enemies[i], bullets[j]) then
130
        table.remove(bullets, j)
131

132
        local thud = sounds.hit:clone()
133
        thud:setPitch(0.9 + math.random() * 0.3)
134
        thud:play()
135

136
        enemies[i].hp = enemies[i].hp - 1
137
        if enemies[i].hp <= 0 then
138
          table.remove(enemies, i)
139
          score = score + 1
140
        end
141
        break
142
      end
143
    end
144
  end
145
end
146

147
local function drawHud()
148
  love.graphics.setColor(1, 1, 1)
149
  love.graphics.print("Score: " .. score, 10, 12)
150

151
  for i = 1, lives do
152
    local x = love.graphics.getWidth() - 24 - (i - 1) * 30
153
    love.graphics.draw(ship, x, 24, 0, 1, 1, ship:getWidth() / 2, ship:getHeight() / 2)
154
  end
155
end
156

157
local function drawOverlay(title, subtitle)
158
  love.graphics.setColor(0, 0, 0, 0.7)
159
  love.graphics.rectangle("fill", 0, 0, love.graphics.getWidth(), love.graphics.getHeight())
160

161
  love.graphics.setColor(1, 1, 1)
162
  love.graphics.setFont(titleFont)
163
  love.graphics.printf(title, 0, 220, love.graphics.getWidth(), "center")
164

165
  love.graphics.setFont(font)
166
  love.graphics.printf(subtitle, 0, 300, love.graphics.getWidth(), "center")
167
end
168

169
function love.draw()
170
  love.graphics.push()
171
  if shake > 0 then
172
    love.graphics.translate(math.random(-6, 6), math.random(-6, 6))
173
  end
174

175
  local blink = invuln > 0 and math.floor(invuln * 10) % 2 == 1
176

177
  if not blink then
178
    love.graphics.setColor(1, 1, 1)
179
    love.graphics.draw(ship, player.x, player.y, 0, 2, 2, ship:getWidth() / 2, ship:getHeight() / 2)
180
  end
181

182
  love.graphics.setColor(1, 0.9, 0.3)
183
  for _, b in ipairs(bullets) do
184
    love.graphics.rectangle("fill", b.x - 2, b.y - 8, 4, 16)
185
  end
186

187
  for _, e in ipairs(enemies) do
188
    e:draw()
189
  end
190

191
  love.graphics.pop()
192

193
  drawHud()
194

195
  if gameState == "menu" then
196
    drawOverlay("SKYNEST", "Press space to play")
197
  elseif gameState == "gameover" then
198
    drawOverlay("GAME OVER", "Score " .. score .. " - press space to play again")
199
  end
200
end

Challenge (Optional)

A scrolling starfield. Build a table of sixty stars with an x, a y and a speed in resetGame, move them down in update, and wrap them to the top when they pass the bottom. Draw them first, before anything else. It is entirely Unit 1 — a list of tables and a loop — and it transforms how the game looks. Give the faster ones a brighter color and you have parallax for free.
Flash an enemy white when it is hit. Give it a flash field, set it to 0.06 on a hit, count it down in Enemy:update and pick the color in Enemy:draw. All of it lands in enemy.lua, which is Activity 2.8 paying you back.
Add music. Find a loop you like, load it with "stream" rather than "static", call setLooping(true), and start it in love.load. It must not be cloned and it must not be restarted on every new game.
Mute on the m key. love.audio.setVolume(0) silences everything at once, including clones that do not exist yet. Keep a boolean and flip it in love.keypressed — and note this is one of the few times a boolean really is the right shape, because there is no timer underneath it to derive the answer from.

Check Your Work

Held fire is a steady stream of shots, not a stutter. Every trigger pull makes a noise.
Hits are audibly different from each other, because each one is a clone with its own pitch.
Losing a life sounds heavy and the world lurches for four tenths of a second. The score and the life icons do not move.
The shaking stops, including on the hit that ends the run.

If half your shots are silent, you skipped clone(). If the game will not start at all, check that all three .wav files are beside main.lua and that both arguments are present in newSource — the type is not optional. If the HUD shakes with the world, it is inside the push and pop. And if the screen never stops shaking after the last life, the countdown is below the early return.

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