add engine burn

asteroids/actors.lua

@@ -91,6 +91,9 @@ function actors.buildActors(game)
         for k, v in pairs(ship) do
             instance[k] = v
         end
+        instance.engineSound = love.audio.newSource(instance.engineSound)
+        instance.engineSound:setVolume(0)
+        instance.engineSound:setLooping(true)
         setmetatable(instance, ships_mt)
         return instance
     end

asteroids/main.lua

@@ -18,6 +18,7 @@ local function initGame()
             },
             sprite = love.graphics.newImage('resources/playerShip1_blue.png'),
             maxThrust = 200,
+            engineSound = love.sound.newSoundData('resources/enginehum3.ogg'),
         },
         asteroids = {
             stages = {
@@ -78,6 +79,12 @@ end
 local state = {}
 
 local function reset()
+    if state.ship then
+        state.ship.engineSound:stop()
+        for _, bullet in ipairs(state.bullets) do
+            bullet.sound:stop()
+        end
+    end
     state = initState()
 end
 
@@ -98,6 +105,17 @@ function love.update(dt)
         if state.ship.throttle > 0 then
             local speed = state.ship.throttle * state.ship.maxThrust * dt
             phys.apply(state.ship, { speed = speed, angle = state.ship.facing })
+            if not state.ship.engineSound:isPlaying() then
+                state.ship.engineSound:play()
+            end
+        end
+        state.ship.engineSound:setVolume(state.ship.throttle * 0.5)
+        -- TODO which is better, keeping the sound playing looping at 0 or checking the
+        -- state each update?
+        if state.ship.throttle == 0 then
+            if state.ship.engineSound:isPlaying() then
+                state.ship.engineSound:stop()
+            end
         end
 
         local spin = state.controls.joystick:getGamepadAxis('leftx') * game.controls.ship.turnRate