v0.1.0 initial commit

audio/synth.go

@@ -0,0 +1,81 @@
+package audio
+
+import (
+	"bytes"
+	"encoding/binary"
+	"math"
+)
+
+const sampleRate = 48000 // PipeWire native rate
+
+// seg is one tone segment: linear frequency sweep with pluck envelope
+type seg struct {
+	f0, f1 float64 // Hz
+	dur    float64 // seconds
+	amp    float64 // 0..1
+	square bool
+}
+
+// effectSegs defines each effect's tone sequence — the tuning surface
+var effectSegs = [EffectCount][]seg{
+	EffectPickup:      {{988, 988, 0.055, 0.5, false}, {1319, 1319, 0.11, 0.5, false}},   // B5→E6 coin
+	EffectMagnet:      {{523, 1319, 0.10, 0.45, false}, {784, 1976, 0.16, 0.4, false}},   // rising double sweep — reads as a suction, distinct from the coin
+	EffectShield:      {{659, 988, 0.07, 0.45, false}, {1319, 1319, 0.16, 0.40, false}},  // chime up into a held tone — armor
+	EffectShieldBreak: {{1200, 300, 0.06, 0.50, true}, {700, 180, 0.14, 0.45, true}},     // square shatter; brighter and shorter than the death crunch
+	EffectBoost:       {{392, 1568, 0.16, 0.50, false}, {1568, 1568, 0.10, 0.35, false}}, // fast sweep up — tempo kick
+	EffectDeflect:     {{1200, 1600, 0.025, 0.20, true}, {1600, 900, 0.035, 0.15, true}}, // fires once per walled chord traversed under a Boost — short, dry, low
+	EffectMoveRow:     {{300, 620, 0.07, 0.35, false}},                                   // whoosh up
+	EffectMoveLane:    {{440, 470, 0.04, 0.28, false}},                                   // tick
+	EffectHitWall:     {{140, 50, 0.30, 0.6, true}},                                      // crunch drop
+	EffectLevelClear: { // C-major arpeggio
+		{523, 523, 0.09, 0.45, false},
+		{659, 659, 0.09, 0.45, false},
+		{784, 784, 0.09, 0.45, false},
+		{1047, 1047, 0.18, 0.45, false},
+	},
+}
+
+// synth renders segments to 16-bit mono PCM
+func synth(segs []seg) []int16 {
+	var out []int16
+	for _, s := range segs {
+		n := int(s.dur * sampleRate)
+		phase := 0.0
+		for i := range n {
+			t := float64(i) / float64(n)
+			f := s.f0 + (s.f1-s.f0)*t
+			phase += 2 * math.Pi * f / sampleRate
+			v := math.Sin(phase)
+			if s.square {
+				if v >= 0 {
+					v = 1
+				} else {
+					v = -1
+				}
+			}
+			env := math.Min(t*24, 1) * math.Exp(-4.2*t) // fast attack, pluck decay
+			out = append(out, int16(v*env*s.amp*32767))
+		}
+	}
+	return out
+}
+
+// wavBytes wraps PCM in a minimal RIFF/WAVE container (PCM16 mono)
+func wavBytes(samples []int16) []byte {
+	var b bytes.Buffer
+	dataLen := uint32(len(samples) * 2)
+	b.WriteString("RIFF")
+	binary.Write(&b, binary.LittleEndian, 36+dataLen)
+	b.WriteString("WAVEfmt ")
+	binary.Write(&b, binary.LittleEndian, uint32(16))
+	binary.Write(&b, binary.LittleEndian, uint16(1)) // PCM
+	binary.Write(&b, binary.LittleEndian, uint16(1)) // mono
+	binary.Write(&b, binary.LittleEndian, uint32(sampleRate))
+	binary.Write(&b, binary.LittleEndian, uint32(sampleRate*2)) // byte rate
+	binary.Write(&b, binary.LittleEndian, uint16(2))            // block align
+	binary.Write(&b, binary.LittleEndian, uint16(16))           // bits/sample
+	b.WriteString("data")
+	binary.Write(&b, binary.LittleEndian, dataLen)
+	binary.Write(&b, binary.LittleEndian, samples)
+	return b.Bytes()
+}