Add item pickup sound.

sound/Makefile

@@ -1,4 +1,4 @@
-SFX = plasma explode explode2 explode3 explode4
+SFX = plasma explode explode2 explode3 explode4 laser item
 OGG = $(SFX:%=%.ogg)
 WAV = $(SFX:%=%.wav)
 

sound/item.csd

@@ -0,0 +1,37 @@
+<CsoundSynthesizer>
+<CsInstruments>
+sr = 48000
+ksmps = 32
+nchnls = 1
+0dbfs = 1
+
+; Item sound:
+; Four notes mixed together and some reverberation added.
+; The notes are sine waves with a very short attack and decay applied,
+; necessary to avoid clicking sounds.
+
+gisine ftgen 1, 0, 16384, 10, 1
+ga1 init 0
+
+instr 1
+	a1 poscil 0.4, p4, gisine
+	a2 linseg 0, 0.001, 1, p3 - 0.002, 1, 0.001, 0
+	ga1 = ga1 + a1 * a2
+endin
+
+instr 99
+	a1 reverb ga1, 0.7
+	out ga1 + a1 * 0.15
+	ga1 = 0
+endin
+</CsInstruments>
+<CsScore>
+i 1 0.00 0.15 300
+i 1 0.08 0.15 450
+i 1 0.16 0.15 375
+i 1 0.24 0.15 600
+i 99 0 0.65
+e
+</CsScore>
+</CsoundSynthesizer>
+