diff --git a/src/main.c b/src/main.c
index 143653a..a5faac7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -24,8 +24,6 @@
 // types and forward declarations
 // --------------------------------------------------------------------
 
-#define array_length(x) (sizeof(x) / sizeof((x)[0]))
-
 typedef int8_t  	i8;
 typedef uint8_t 	u8;
 typedef uint16_t	u16;
@@ -44,11 +42,15 @@ typedef void (*keyfunc)(keycode, bool);
 
 #include "./keyboard/layout.c"
 // defines:
-// #define KB_Layers #{Layers.size}
+// #define KB_LAYERS #{Layers.size}
 // static const keycode	PROGMEM _kb_layout[KB_LAYERS][KB_ROWS][KB_COLUMNS];
 // static const keyfunc	PROGMEM _kb_layout_press[KB_LAYERS][KB_ROWS][KB_COLUMNS];
 // static const keyfunc	PROGMEM _kb_layout_release[KB_LAYERS][KB_ROWS][KB_COLUMNS];
 
+#if KB_LAYERS > 8
+#error can only handle 8 layers for now
+#endif
+
 // ----------------------------------------------------------------------------
 // globals
 // ----------------------------------------------------------------------------
@@ -63,6 +65,7 @@ static layer	layers_pressed[KB_ROWS][KB_COLUMNS];
 
 static i8   	layers_active[KB_LAYERS];
 static layer	layers_top;
+static u8   	layers_state;
 
 static bool	layer_sticky_on;
 static bool	layer_sticky[KB_LAYERS];
@@ -80,6 +83,24 @@ static const keyfunc _kb_layer_funcs[] = {
   &kbfun_win_layer_press_release,
 };
 
+// ----------------------------------------------------------------------------
+// utilities
+// ----------------------------------------------------------------------------
+
+#define array_length(x) (sizeof(x) / sizeof((x)[0]))
+
+#define set_bit(x, i)   	(x) |= (1u << (i))
+#define unset_bit(x, i) 	(x) &= ~(1u << (i))
+#define toggle_bit(x, i)	(x) ^= (1u << (i))
+#define is_set(x, i)    	(((x) >> (i)) & 1u)
+#define is_unset(x, i)  	!is_set((x), (i))
+
+#define set_layer(x, layer)   	set_bit((x), (layer) - 1)
+#define unset_layer(x, layer) 	unset_bit((x), (layer) - 1)
+#define toggle_layer(x, layer)	toggle_bit((x), (layer) - 1)
+
+// ----------------------------------------------------------------------------
+// main
 // ----------------------------------------------------------------------------
 
 int main() {
@@ -93,8 +114,6 @@ int main() {
   return 0;
 }
 
-// --------------------------------------------------------------------------------------
-
 void main_key_loop() {
   for (;;) {
     // swap `kb_is_pressed` and `kb_was_pressed`, then update
@@ -182,6 +201,7 @@ void init_layers() {
   }
   layers_active[0]	= 1;
   layers_top      	= 0;
+  layers_state    	= 1;
 
   for (u8 row=0; row<KB_ROWS; row++) {
     for (u8 col=0; col<KB_COLUMNS; col++) {
@@ -198,6 +218,7 @@ void init_layers() {
 layer highest_active_layer() {
   for (layer l = KB_LAYERS - 1; l > 0; l--) {
     if (layers_active[l] > 0) { return l; }
+    /* if (is_set(layers_state, l)) { return l; } */
   }
 
   // the base layer is always active
@@ -209,6 +230,7 @@ void layer_enable(layer l) {
   if (l >= KB_LAYERS || l == 0) { return; }
 
   layers_active[l] += 1;
+  set_layer(layers_state, l);
 
   if (l > layers_top) {
     layers_top = l;
@@ -223,6 +245,9 @@ void layer_disable(layer l) {
   if (layers_active[l] > 0) {
     layers_active[l] -= 1;
   }
+  if (layers_active[l] == 0) {
+    unset_layer(layers_state, l);
+  }
 
   if (l == layers_top) {
     layers_top = highest_active_layer();
@@ -305,9 +330,9 @@ void _kbfun_mediakey_press_release(keycode key, bool is_pressed) {
 
 void _kbfun_modifier_press_release(keycode key, bool is_pressed) {
   if (is_pressed) {
-    keyboard_modifier_keys |= (1<<key);
+    set_bit(keyboard_modifier_keys, key);
   } else {
-    keyboard_modifier_keys &= ~(1<<key);
+    unset_bit(keyboard_modifier_keys, key);
   }
 }
 
@@ -326,7 +351,7 @@ bool _kbfun_mediakey_is_pressed(keycode key) {
 }
 
 bool _kbfun_modifier_is_pressed(keycode key) {
-  return (keyboard_modifier_keys & (1<<key));
+  return is_set(keyboard_modifier_keys, key);
 }
 
 void _kbfun_normal_sticky_done() {
@@ -411,8 +436,8 @@ void kbfun_modifier_sticky(keycode key, bool is_pressed) {
     if (mod_sticky_done) {
       kbfun_modifier_press_release(key, false);
     } else {
-      mod_sticky     	|= 1<<mod;
-      mod_sticky_done	= false;
+      set_bit(mod_sticky, mod);
+      mod_sticky_done = false;
     }
   }
 }