diff --git a/const.h b/const.h
index a446624..7d319d3 100644
--- a/const.h
+++ b/const.h
@@ -16,4 +16,10 @@
 
 #define SAMPLE_RATE 44100.0f
 
+#define BPM_MIN 30.0f
+#define BPM_MAX 300.0f
+#define VCO_MIN 40.0f
+#define VCO_MAX 3200.0f
+
 #define otherwise else
+
diff --git a/state.h b/state.h
index 3492876..d627b91 100644
--- a/state.h
+++ b/state.h
@@ -1,7 +1,8 @@
 #pragma once
 
 #include <stdint.h>
-#include "vco.h"
+#include <stdbool.h>
+#include "vco.hh"
 
 typedef struct {
 	union {