diff --git a/firmware/keyboard.h b/firmware/keyboard.h
index a545776..33eec9c 100644
--- a/firmware/keyboard.h
+++ b/firmware/keyboard.h
@@ -45,6 +45,14 @@ void kb__led__set (uint8_t led, float n);
 // -------
 bool kb__led__read (uint8_t led);
 // -------
+#ifdef ENABLE_LEFT_LED
+uint8_t kb__led__flicker (uint8_t led);
+uint8_t kb__led__flicker_peek (uint8_t led);
+#endif
+#ifdef ENABLE_TEENSY_LED
+uint8_t kb__led__dbg_blink (uint8_t blinks);
+#endif
+// -------
 void kb__led__all_on  (void);
 void kb__led__all_off (void);
 void kb__led__all_set (float percent);
diff --git a/firmware/keyboard/ergodox/controller/mcp23018.c b/firmware/keyboard/ergodox/controller/mcp23018.c
index 7b78714..3a20cd0 100644
--- a/firmware/keyboard/ergodox/controller/mcp23018.c
+++ b/firmware/keyboard/ergodox/controller/mcp23018.c
@@ -66,6 +66,12 @@
 #define  TWI_ADDR_WRITE  ( (TWI_ADDR<<1) | TW_WRITE )
 #define  TWI_ADDR_READ   ( (TWI_ADDR<<1) | TW_READ  )
 
+#ifdef ENABLE_LEFT_LED
+#define LED_11_BIT_SHIFT    7  // in B
+#define LED_12_BIT_SHIFT    6  // in B
+#define LED_13_BIT_SHIFT    7  // in A
+#endif
+
 // ----------------------------------------------------------------------------
 
 /**                                        functions/mcp23018__init/description
@@ -91,11 +97,21 @@ uint8_t mcp23018__init(void) {
     if (ret) goto out;  // make sure we got an ACK
     twi__send(IODIRA);
     #if OPT__MCP23018__DRIVE_ROWS
+#ifndef ENABLE_LEFT_LED
         twi__send(0b11111111);  // IODIRA
         twi__send(0b11000000);  // IODIRB
+#else
+        twi__send(0b01111111);  // IODIRA
+        twi__send(0b00000000);  // IODIRB
+#endif
     #elif OPT__MCP23018__DRIVE_COLUMNS
+#ifndef ENABLE_LEFT_LED
         twi__send(0b10000000);  // IODIRA
         twi__send(0b11111111);  // IODIRB
+#else
+        twi__send(0b00000000);  // IODIRA
+        twi__send(0b00111111);  // IODIRB
+#endif
     #endif
     twi__stop();
 
@@ -108,11 +124,21 @@ uint8_t mcp23018__init(void) {
     if (ret) goto out;  // make sure we got an ACK
     twi__send(GPPUA);
     #if OPT__MCP23018__DRIVE_ROWS
+#ifndef ENABLE_LEFT_LED
         twi__send(0b11111111);  // GPPUA
         twi__send(0b11000000);  // GPPUB
+#else
+        twi__send(0b01111111);  // GPPUA
+        twi__send(0b00000000);  // GPPUB
+#endif
     #elif OPT__MCP23018__DRIVE_COLUMNS
+#ifndef ENABLE_LEFT_LED
         twi__send(0b10000000);  // GPPUA
         twi__send(0b11111111);  // GPPUB
+#else
+        twi__send(0b00000000);  // GPPUA
+        twi__send(0b00111111);  // GPPUB
+#endif
     #endif
     twi__stop();
 
@@ -124,8 +150,14 @@ uint8_t mcp23018__init(void) {
     ret = twi__send(TWI_ADDR_WRITE);
     if (ret) goto out;  // make sure we got an ACK
     twi__send(OLATA);
+#ifndef ENABLE_LEFT_LED
     twi__send(0b11111111);  //OLATA
     twi__send(0b11111111);  //OLATB
+#else
+    twi__send(0b11111111 & ~(kb__led__flicker(13)<<LED_13_BIT_SHIFT));  //OLATA
+    twi__send(0b11111111 & ~(kb__led__flicker(11)<<LED_11_BIT_SHIFT) & \
+              ~(kb__led__flicker(12)<<LED_12_BIT_SHIFT));  //OLATB
+#endif
 
 out:
     twi__stop();
@@ -164,7 +196,13 @@ uint8_t mcp23018__update_matrix(bool matrix[OPT__KB__ROWS][OPT__KB__COLUMNS]) {
 
     // update our part of the matrix ..........................................
 
-    #if OPT__MCP23018__DRIVE_ROWS
+#ifdef ENABLE_LEFT_LED
+    // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+    // For some reason as yet unknown, if an LED is lit on a port that is scanned
+    // the twi__read will hang.
+#endif
+
+#if OPT__MCP23018__DRIVE_ROWS
         for (uint8_t row=0; row<=5; row++) {
             // set active row low  : 0
             // set other rows hi-Z : 1
@@ -193,7 +231,13 @@ uint8_t mcp23018__update_matrix(bool matrix[OPT__KB__ROWS][OPT__KB__COLUMNS]) {
         twi__start();
         twi__send(TWI_ADDR_WRITE);
         twi__send(GPIOB);
+#ifndef ENABLE_LEFT_LED
         twi__send(0xFF);
+#else
+        twi__send(0xFF & \
+                  ~(kb__led__flicker_peek(11)<<LED_11_BIT_SHIFT) & \
+                  ~(kb__led__flicker_peek(12)<<LED_12_BIT_SHIFT));
+#endif
         twi__stop();
 
     #elif OPT__MCP23018__DRIVE_COLUMNS
@@ -225,7 +269,11 @@ uint8_t mcp23018__update_matrix(bool matrix[OPT__KB__ROWS][OPT__KB__COLUMNS]) {
         twi__start();
         twi__send(TWI_ADDR_WRITE);
         twi__send(GPIOA);
+#ifndef ENABLE_LEFT_LED
         twi__send(0xFF);
+#else
+        twi__send(0xFF & ~(kb__led__flicker_peek(13)<<LED_13_BIT_SHIFT));
+#endif
         twi__stop();
 
     #endif
@@ -234,4 +282,3 @@ uint8_t mcp23018__update_matrix(bool matrix[OPT__KB__ROWS][OPT__KB__COLUMNS]) {
 
     return ret;  // success
 }
-
diff --git a/firmware/keyboard/ergodox/controller/teensy-2-0.c b/firmware/keyboard/ergodox/controller/teensy-2-0.c
index b0a98a0..8905421 100644
--- a/firmware/keyboard/ergodox/controller/teensy-2-0.c
+++ b/firmware/keyboard/ergodox/controller/teensy-2-0.c
@@ -200,21 +200,31 @@ uint8_t teensy__init(void) {
     CPU_PRESCALE(CPU_16MHz);
 
     // onboard LED
-    // (tied to GND for hardware convenience)
+#ifndef ENABLE_TEENSY_LED
     DDRD  &= ~(1<<6);  // set D(6) as input
+#else
+    DDRD |= (1<<6);    // set D(6) as output
+#endif
     PORTD &= ~(1<<6);  // set D(6) internal pull-up disabled
 
     // (tied to Vcc for hardware convenience)
     DDRB  &= ~(1<<4);  // set B(4) as input
     PORTB &= ~(1<<4);  // set B(4) internal pull-up disabled
 
+#ifdef ENABLE_LEFT_LED
+    // I2C (TWI)
+    twi__init();  // on pins D(1,0)
+#endif
+
     // keyboard LEDs (see "PWM on ports OC1(A|B|C)" in "teensy-2-0.md")
     kb__led__all_off();  // (just to put the pins in a known state)
     TCCR1A  = 0b10101001;  // set and configure fast PWM
     TCCR1B  = 0b00001001;  // set and configure fast PWM
 
+#ifndef ENABLE_LEFT_LED
     // I2C (TWI)
     twi__init();  // on pins D(1,0)
+#endif
 
     // unused pins
     teensypin_write_all_unused(DDR, CLEAR); // set as input
diff --git a/firmware/keyboard/ergodox/layout/common/keys.c.h b/firmware/keyboard/ergodox/layout/common/keys.c.h
index 83682d6..9a9c855 100644
--- a/firmware/keyboard/ergodox/layout/common/keys.c.h
+++ b/firmware/keyboard/ergodox/layout/common/keys.c.h
@@ -98,9 +98,35 @@
  *   side "press" function names will themselves have been expanded by the
  *   `P()` macro; but I'm not really sure why that makes a difference.
  */
+#ifdef ENABLE_LEFT_LED_LAYERS
+static void set_layer_leds(uint8_t l)
+{
+    kb__led__off(11);
+    kb__led__off(12);
+    kb__led__off(13);
+    switch(l) {
+        case 1: kb__led__on(13); break;
+        case 2: kb__led__on(12); break;
+        case 3: kb__led__on(11); break;
+    }
+}
+#endif
+
+#ifndef ENABLE_LEFT_LED_LAYERS
 #define  KEYS__LAYER__PUSH_POP(ID, LAYER)                                   \
     void P(lpupo##ID##l##LAYER) (void) { layer_stack__push(0, ID, LAYER); } \
     void R(lpupo##ID##l##LAYER) (void) { layer_stack__pop_id(ID); }
+#else
+#define  KEYS__LAYER__PUSH_POP(ID, LAYER)                                   \
+    void P(lpupo##ID##l##LAYER) (void) {                                    \
+        layer_stack__push(0, ID, LAYER);                                    \
+        set_layer_leds(layer_stack__peek(0));                               \
+    }                                                                       \
+    void R(lpupo##ID##l##LAYER) (void) {                                    \
+        layer_stack__pop_id(ID);                                            \
+        set_layer_leds(layer_stack__peek(0));                               \
+    }
+#endif
 
 /**                               macros/(group) layer : number pad/description
  * Define functions for pushing and popping the number pad (namely `numPush`,
@@ -114,27 +140,59 @@
  * These macros are meant to be used (if necessary) in the layout file, since
  * they need to know the layer on which the number pad has been placed.
  */
+#ifndef ENABLE_LEFT_LED_LAYERS
+#define  KEYS__LAYER__NUM_PU_PO(ID, LAYER)                              \
+    void P(numPuPo) (void) { layer_stack__push(0, ID, LAYER);           \
+                             KF(press)(KEYBOARD__LockingNumLock);       \
+                             usb__kb__send_report();                    \
+                             KF(release)(KEYBOARD__LockingNumLock);     \
+                             usb__kb__send_report(); }                  \
+    void R(numPuPo) (void) { layer_stack__pop_id(ID);                   \
+                             KF(press)(KEYBOARD__LockingNumLock);       \
+                             usb__kb__send_report();                    \
+                             KF(release)(KEYBOARD__LockingNumLock);     \
+                             usb__kb__send_report(); }
+#else
 #define  KEYS__LAYER__NUM_PU_PO(ID, LAYER)                              \
     void P(numPuPo) (void) { layer_stack__push(0, ID, LAYER);           \
+                             set_layer_leds(layer_stack__peek(0));      \
                              KF(press)(KEYBOARD__LockingNumLock);       \
                              usb__kb__send_report();                    \
                              KF(release)(KEYBOARD__LockingNumLock);     \
                              usb__kb__send_report(); }                  \
     void R(numPuPo) (void) { layer_stack__pop_id(ID);                   \
+                             set_layer_leds(layer_stack__peek(0));      \
                              KF(press)(KEYBOARD__LockingNumLock);       \
                              usb__kb__send_report();                    \
                              KF(release)(KEYBOARD__LockingNumLock);     \
                              usb__kb__send_report(); }
+#endif
 
+#ifndef ENABLE_LEFT_LED_LAYERS
+#define  KEYS__LAYER__NUM_PUSH(ID, LAYER)                               \
+    void P(numPush) (void) { layer_stack__push(0, ID, LAYER);           \
+                             KF(press)(KEYBOARD__LockingNumLock); }     \
+    void R(numPush) (void) { KF(release)(KEYBOARD__LockingNumLock); }
+#else
 #define  KEYS__LAYER__NUM_PUSH(ID, LAYER)                               \
     void P(numPush) (void) { layer_stack__push(0, ID, LAYER);           \
+                             set_layer_leds(layer_stack__peek(0));      \
                              KF(press)(KEYBOARD__LockingNumLock); }     \
     void R(numPush) (void) { KF(release)(KEYBOARD__LockingNumLock); }
+#endif
 
+#ifndef ENABLE_LEFT_LED_LAYERS
+#define  KEYS__LAYER__NUM_POP(ID)                                       \
+    void P(numPop) (void) { layer_stack__pop_id(ID);                    \
+                            KF(press)(KEYBOARD__LockingNumLock); }      \
+    void R(numPop) (void) { KF(release)(KEYBOARD__LockingNumLock); }
+#else
 #define  KEYS__LAYER__NUM_POP(ID)                                       \
     void P(numPop) (void) { layer_stack__pop_id(ID);                    \
+                            set_layer_leds(layer_stack__peek(0));       \
                             KF(press)(KEYBOARD__LockingNumLock); }      \
     void R(numPop) (void) { KF(release)(KEYBOARD__LockingNumLock); }
+#endif
 
 // ----------------------------------------------------------------------------
 
diff --git a/firmware/keyboard/ergodox/led.c b/firmware/keyboard/ergodox/led.c
index 761089d..9b981dc 100644
--- a/firmware/keyboard/ergodox/led.c
+++ b/firmware/keyboard/ergodox/led.c
@@ -14,6 +14,9 @@
 #include <stdint.h>
 #include <avr/io.h>
 #include <util/delay.h>
+#ifdef ENABLE_LEFT_LED
+#include "./controller/mcp23018.h"
+#endif
 
 // ----------------------------------------------------------------------------
 
@@ -27,6 +30,38 @@
 
 // ----------------------------------------------------------------------------
 
+#ifdef ENABLE_LEFT_LED
+#define L_TOP    11        // red
+#define L_MID    12        // yellow
+#define L_BOT    13        // green
+
+#define L_MIN    L_TOP     // first LED
+#define L_MAX    L_BOT     // last LED
+
+#define L_IDX(x) (x-L_MIN)
+
+#define L_STEPS   5  // 0%, 25%, 50%, 75%, 100%  (zero is NOT off, just dimmest)
+
+// during power up there is no polling of the mcp23018 so no way to control
+// brightness - it's just on/off
+
+static bool _l_startup;
+
+// state
+
+static bool _l_on[L_MAX-L_MIN+1];
+
+// bright values are 0-(L_STEPS-1)
+
+static uint8_t _l_bright[L_MAX-L_MIN+1];
+
+// cyclic counters for brightness
+
+static uint8_t _l_flicker[L_MAX-L_MIN+1];
+#endif
+
+// ----------------------------------------------------------------------------
+
 void kb__led__on(uint8_t led) {
     switch(led) {
         case 1: (DDRB |=  (1<<5)); break;  // topmost
@@ -34,6 +69,18 @@ void kb__led__on(uint8_t led) {
         case 3: (DDRB |=  (1<<7)); break;  // bottommost
         case 4:                    break;
         case 5:                    break;
+#ifdef ENABLE_TEENSY_LED
+        case 6: (PORTD |=  (1<<6)); break;
+#endif        
+#ifdef ENABLE_LEFT_LED
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            _l_on[L_IDX(led)] = 1;
+            if (_l_startup)
+                mcp23018__init();
+            break;
+#endif	
     };
 }
 
@@ -44,6 +91,18 @@ void kb__led__off(uint8_t led) {
 	    case 3: (DDRB &= ~(1<<7)); break;  // bottommost
         case 4:                    break;
         case 5:                    break;
+#ifdef ENABLE_TEENSY_LED
+        case 6: (PORTD &= ~(1<<6)); break;
+#endif        
+#ifdef ENABLE_LEFT_LED
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            _l_on[L_IDX(led)] = 0;
+            if (_l_startup)
+                mcp23018__init();
+            break;
+#endif	
     };
 }
 
@@ -54,6 +113,13 @@ void kb__led__set(uint8_t led, float n) {
         case 3: (OCR1C = (uint8_t)((n) * 0xFF)); break;  // bottommost
         case 4:                                  break;
         case 5:                                  break;
+#ifdef ENABLE_LEFT_LED
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            _l_bright[L_IDX(led)] = (uint8_t)((n) * (L_STEPS-1));
+            break;
+#endif	
     };
 }
 
@@ -66,46 +132,162 @@ bool kb__led__read(uint8_t led) {
 	    case 3: return (PINB & (1<<7));  // bottommost
         case 4: ;
         case 5: ;
+#ifdef ENABLE_TEENSY_LED
+        case 6: return (PIND & (1<<6));
+#endif        
+#ifdef ENABLE_LEFT_LED
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            return(_l_on[L_IDX(led)]);
+#endif	
     };
     return false;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
+#ifdef ENABLE_LEFT_LED
+static uint8_t kb__led__flicker_peek_bare(uint8_t led)
+{
+    // Light the led every Nth cycle.  N is 1 to L_STEPS.
+
+    switch(led) {
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            return((_l_flicker[L_IDX(led)] % (L_STEPS - _l_bright[L_IDX(led)] + 1)) == 0 ? 1 : 0);
+        default: return(1);
+    };
+}
+
+uint8_t kb__led__flicker_peek(uint8_t led)
+{
+    // See if this is currently a cycle to be lit.
+    // It is called by mcp23018__update_matrix to refresh lit value as it scans the
+    // other bits.  At the top of mcp23018__update_matrix, mcp23018__init is called
+    // so the flicker counters have already been incremented for this cycle.
+
+    if (_l_startup)
+        return(kb__led__read(led));
+
+    if (!kb__led__read(led))
+      return(0);
+
+    return(kb__led__flicker_peek_bare(led));
+}
+
+uint8_t kb__led__flicker(uint8_t led)
+{
+    // mcp23018__init calls this once for each led.  mcp23018__init is called every
+    // scanning cycle.  *_flicker is incremented on each call wrapping after 251 times.
+    // Then we see if it is time to light.
+
+    if (_l_startup)
+        return(kb__led__read(led));
+
+    if (!kb__led__read(led))
+      return(0);
+
+    switch(led) {
+        case L_TOP:
+        case L_MID:
+        case L_BOT:
+            if (_l_flicker[L_IDX(led)]++ == 255) _l_flicker[L_IDX(led)] = 0; break;
+    };
+
+    return(kb__led__flicker_peek_bare(led));
+}
+#endif
+
+#ifdef ENABLE_TEENSY_LED
+uint8_t kb__led__dbg_blink(uint8_t blinks)
+{
+    _delay_ms(500);
+
+    for (uint8_t i = blinks; i; i--) {
+      _delay_ms(250);
+      kb__led__on(6);
+      _delay_ms(250);
+      kb__led__off(6);
+    }
+
+    return(0);
+}
+#endif
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+
 void kb__led__all_on(void) {
     for(int8_t i=1; i<=3; i++)
         kb__led__on(i);
+#ifdef ENABLE_TEENSY_LED
+    kb__led__on(6);
+#endif
+#ifdef ENABLE_LEFT_LED
+    if (!_l_startup)
+        for(uint8_t i=L_MIN; i<=L_MAX; i++)
+            kb__led__on(i);
+#endif
 }
 
 void kb__led__all_off(void) {
     for(int8_t i=1; i<=3; i++)
         kb__led__off(i);
+#ifdef ENABLE_TEENSY_LED
+    kb__led__off(6);
+#endif
+#ifdef ENABLE_LEFT_LED
+    for(uint8_t i=L_MIN; i<=L_MAX; i++)
+        kb__led__off(i);
+#endif
 }
 
 void kb__led__all_set(float n) {
     for(int8_t i=1; i<=3; i++)
         kb__led__set(i, n);
+#ifdef ENABLE_LEFT_LED
+    for(uint8_t i=L_MIN; i<=L_MAX; i++)
+        kb__led__set(i, n);
+#endif
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
 void kb__led__state__power_on(void) {
+#ifdef ENABLE_LEFT_LED
+    _l_startup = 1;
+#endif  
     kb__led__all_set( OPT__LED_BRIGHTNESS / 10 );
     kb__led__all_on();
 }
 
 void kb__led__state__ready(void) {
+#ifdef ENABLE_LEFT_LED
+    _l_startup = 0;
+#endif  
     kb__led__all_off();
     kb__led__all_set( OPT__LED_BRIGHTNESS );
 }
 
 void kb__led__delay__usb_init(void) {
+#ifdef ENABLE_TEENSY_LED
+    kb__led__off(6);
+#endif
 	// need to delay for a total of ~1 second
     kb__led__set( 1, OPT__LED_BRIGHTNESS );
+#ifdef ENABLE_LEFT_LED
+    kb__led__on( L_TOP );
+#endif
     _delay_ms(333);
     kb__led__set( 2, OPT__LED_BRIGHTNESS );
+#ifdef ENABLE_LEFT_LED
+    kb__led__on( L_MID );
+#endif
     _delay_ms(333);
     kb__led__set( 3, OPT__LED_BRIGHTNESS );
+#ifdef ENABLE_LEFT_LED
+    kb__led__on( L_BOT );
+#endif
     _delay_ms(333);
 }
-
diff --git a/firmware/makefile b/firmware/makefile
index c829ea8..5468b2a 100644
--- a/firmware/makefile
+++ b/firmware/makefile
@@ -64,6 +64,7 @@ SRC += $(wildcard $(CURDIR)/main.c)
 
 # -----------------------------------------------------------------------------
 
+CFLAGS += -DENABLE_TEENSY_LED -DENABLE_LEFT_LED -DENABLE_LEFT_LED_LAYERS
 CFLAGS += -mmcu=$(MCU)      # processor type; must match real life
 CFLAGS += -DF_CPU=$(F_CPU)  # processor frequency; must match initialization
 			    #   in source