1 files changed, 40 insertions, 0 deletions
diff --git a/engine/sine.asm b/engine/sine.asm
new file mode 100644
index 00000000..4341e848
--- /dev/null
+++ b/engine/sine.asm
@@ -0,0 +1,40 @@
+Sine_e:: ; 8ac9 (2:4ac9)
+	ld a, e
+	and $3f
+	cp $20
+	jr nc, .negative
+	call .GetSine
+	ld a, h
+	ret
+.negative
+	and $1f
+	call .GetSine
+	ld a, h
+	xor $ff
+	inc a
+	ret
+
+.GetSine: ; 8adf (2:4adf)
+	ld e, a
+	ld a, d
+	ld d, $0
+	ld hl, .SineWave
+	add hl, de
+	add hl, de
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	ld hl, $0
+.loop
+	srl a
+	jr nc, .no_add
+	add hl, de
+.no_add
+	sla e
+	rl d
+	and a
+	jr nz, .loop
+	ret
+
+.SineWave:
+	sine_wave $100