diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
index 9fce3b64..b5e7b034 100644
--- a/app/CMakeLists.txt
+++ b/app/CMakeLists.txt
@@ -25,7 +25,6 @@ zephyr_linker_sources(RODATA include/linker/zmk-events.ld)
 target_include_directories(app PRIVATE include)
 target_sources(app PRIVATE src/kscan.c)
 target_sources(app PRIVATE src/matrix_transform.c)
-target_sources(app PRIVATE src/keymap.c)
 target_sources(app PRIVATE src/hid.c)
 target_sources(app PRIVATE src/sensors.c)
 target_sources_ifdef(CONFIG_ZMK_DISPLAY app PRIVATE src/display.c)
@@ -37,11 +36,13 @@ target_sources(app PRIVATE src/events/sensor_event.c)
 target_sources(app PRIVATE src/behaviors/behavior_key_press.c)
 target_sources(app PRIVATE src/behaviors/behavior_reset.c)
 target_sources(app PRIVATE src/behaviors/behavior_mod_tap.c)
+target_sources(app PRIVATE src/behaviors/behavior_tap_hold.c)
 target_sources(app PRIVATE src/behaviors/behavior_momentary_layer.c)
 target_sources(app PRIVATE src/behaviors/behavior_toggle_layer.c)
 target_sources(app PRIVATE src/behaviors/behavior_transparent.c)
 target_sources(app PRIVATE src/behaviors/behavior_none.c)
 target_sources(app PRIVATE src/behaviors/behavior_sensor_rotate_key_press.c)
+target_sources(app PRIVATE src/keymap.c)
 target_sources_ifdef(CONFIG_ZMK_RGB_UNDERGLOW app PRIVATE src/behaviors/behavior_rgb_underglow.c)
 target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/ble.c)
 target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/ble_unpair_combo.c)
diff --git a/app/dts/bindings/behaviors/zmk,behavior-tap-hold.yaml b/app/dts/bindings/behaviors/zmk,behavior-tap-hold.yaml
new file mode 100644
index 00000000..d6d041b0
--- /dev/null
+++ b/app/dts/bindings/behaviors/zmk,behavior-tap-hold.yaml
@@ -0,0 +1,23 @@
+# Copyright (c) 2020, Cody McGinnis; Okke Formsma
+# SPDX-License-Identifier: MIT
+
+description: Hold or Tap behavior
+
+compatible: "zmk,behavior-tap-hold"
+
+include: zero_param.yaml
+
+properties:
+  bindings:
+    type: phandle-array
+    required: true
+  tapping_term_ms:
+    type: int 
+  flavor:
+    type: string
+    required: false
+    default: "hold-preferred"
+    enum:
+    - "hold-preferred"
+    - "balanced"
+    - "tap-preferred"
\ No newline at end of file
diff --git a/app/include/zmk/event-manager.h b/app/include/zmk/event-manager.h
index 43d3f299..07c0aa98 100644
--- a/app/include/zmk/event-manager.h
+++ b/app/include/zmk/event-manager.h
@@ -78,6 +78,10 @@ struct zmk_event_subscription {
 #define ZMK_EVENT_RELEASE(ev) \
     zmk_event_manager_release((struct zmk_event_header *)ev);
 
+#define ZMK_EVENT_RELEASE_AGAIN(ev) \
+    zmk_event_manager_release_again((struct zmk_event_header *)ev);
+
 int zmk_event_manager_raise(struct zmk_event_header *event);
 int zmk_event_manager_raise_after(struct zmk_event_header *event, const struct zmk_listener *listener);
 int zmk_event_manager_release(struct zmk_event_header *event);
+int zmk_event_manager_release_again(struct zmk_event_header *event);
diff --git a/app/src/behaviors/behavior_tap_hold.c b/app/src/behaviors/behavior_tap_hold.c
new file mode 100644
index 00000000..459d1c3c
--- /dev/null
+++ b/app/src/behaviors/behavior_tap_hold.c
@@ -0,0 +1,432 @@
+/*
+ * Copyright (c) 2020 Cody McGinnis, Okke Formsma
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT zmk_behavior_tap_hold
+
+#include <device.h>
+#include <drivers/behavior.h>
+#include <logging/log.h>
+#include <zmk/behavior.h>
+
+#include <zmk/matrix.h>
+#include <zmk/endpoints.h>
+#include <zmk/event-manager.h>
+#include <zmk/events/position-state-changed.h>
+#include <zmk/events/keycode-state-changed.h>
+#include <zmk/events/modifiers-state-changed.h>
+#include <zmk/hid.h>
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#if DT_NODE_EXISTS(DT_DRV_INST(0))
+
+/************************************************************  DATA SETUP */
+#define ZMK_BHV_TAP_HOLD_MAX_HELD 10
+#define ZMK_BHV_TAP_HOLD_MAX_CAPTURED_KC 40
+
+#define TH_TYPE_MOD_PREFERRED 0
+#define TH_TYPE_BALANCED 1
+#define TH_TYPE_TAP_PREFERRED 2
+
+
+// increase if you have keyboard with more keys.
+#define TH_POSITION_NOT_USED 9999 
+
+struct behavior_tap_hold_behaviors {
+  struct zmk_behavior_binding tap;
+  struct zmk_behavior_binding hold;
+};
+
+typedef k_timeout_t (*timer_func)();
+
+struct behavior_tap_hold_config {
+  timer_func tapping_term_ms;
+  struct behavior_tap_hold_behaviors* behaviors;
+  char* flavor;
+};
+
+// this data is specific for each tap-hold
+struct active_tap_hold {
+  s32_t position;
+  bool is_decided;
+  bool is_hold;
+  const struct behavior_tap_hold_config *config;
+  struct k_delayed_work work;
+  bool work_is_cancelled;
+};
+
+struct active_tap_hold* undecided_tap_hold = NULL;
+struct active_tap_hold active_tap_holds[ZMK_BHV_TAP_HOLD_MAX_HELD] = {};
+struct position_state_changed* captured_position_events[ZMK_BHV_TAP_HOLD_MAX_CAPTURED_KC] = {};
+
+/************************************************************  CAPTURED POSITION HELPER FUNCTIONS */
+int capture_position_event(struct position_state_changed* event) {
+  for (int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_CAPTURED_KC; i++) {
+    if (captured_position_events[i] == NULL) {
+      captured_position_events[i] = event;
+      return 0;
+    }
+  }
+  return -ENOMEM;
+}
+
+struct position_state_changed* find_captured_keydown_event(u32_t position)
+{
+  struct position_state_changed *last_match = NULL;
+  for (int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_CAPTURED_KC; i++) {
+    struct position_state_changed* event = captured_position_events[i];
+    if (event == NULL) {
+      return last_match;
+    }
+
+    if (captured_position_events[i]->position == position && captured_position_events[i]->state) {
+      last_match = event;
+    }
+  }
+
+  return last_match;
+}
+
+int behavior_tap_hold_listener(const struct zmk_event_header *eh);
+void release_captured_positions() {
+  if (undecided_tap_hold != NULL) {
+    return;
+  }
+
+  // We use a trick to prevent copying the captured_position_events array.
+  //
+  // Events for different mod-tap instances are separated by a NULL pointer.
+  //
+  // The first event popped will never be catched by the next active tap-hold
+  // because to start capturing a mod-tap-key-down event must first completely
+  // go through the events queue.
+  // 
+  // Example of this release process;
+  // [mt2_down, k1_down, k1_up, mt2_up, null, ...]
+  //  ^
+  // mt2_down position event isn't captured because no tap-hold is active.
+  // mt2_down behavior event is handled, now we have an undecided tap-hold
+  // [null, k1_down, k1_up, mt2_up, null, ...]
+  //        ^
+  // k1_down  is captured by the mt2 mod-tap
+  // !note that searches for find_captured_position_event by the mt2 behavior will stop at the first null encountered
+  // [mt1_down, null, k1_up, mt2_up, null, ...]
+  //                  ^
+  // k1_up event is captured by the new tap-hold:
+  // [k1_down, k1_up, null, mt2_up, null, ...]
+  //                        ^
+  // mt2_up event is not captured but causes release of mt2 behavior
+  // [k1_down, k1_up, null, null, null, ...]
+  // now mt2 will start releasing it's own captured positions.
+  for(int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_CAPTURED_KC; i++) {
+    struct position_state_changed* captured_position = captured_position_events[i];
+    if(captured_position == NULL) {
+      return;
+    }
+    captured_position_events[i] = NULL;
+    if(undecided_tap_hold != NULL) {
+      k_msleep(10);
+    }
+    LOG_DBG("Releasing key position event for position %d %s", captured_position->position, (captured_position->state ? "pressed" : "released"));
+    ZMK_EVENT_RELEASE_AGAIN(captured_position);
+  }
+}
+
+
+/************************************************************  ACTIVE TAP HOLD HELPER FUNCTIONS */
+
+struct active_tap_hold* find_tap_hold(u32_t position) 
+{
+  for (int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_HELD; i++) {
+    if (active_tap_holds[i].position == position) {
+      return &active_tap_holds[i];
+    }
+  }
+  return NULL;
+}
+
+struct active_tap_hold* store_tap_hold(u32_t position, const struct behavior_tap_hold_config* config) 
+{
+  for (int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_HELD; i++) {
+    if (active_tap_holds[i].position != TH_POSITION_NOT_USED) {
+      continue;
+    }
+    active_tap_holds[i].position = position;
+    active_tap_holds[i].is_decided = false;
+    active_tap_holds[i].is_hold = false;
+    active_tap_holds[i].config = config;
+    return &active_tap_holds[i];
+  }
+  return NULL;
+}
+
+void clear_tap_hold(struct active_tap_hold * tap_hold) 
+{
+  tap_hold->position = TH_POSITION_NOT_USED;
+  tap_hold->is_decided = false;
+  tap_hold->is_hold = false;
+  tap_hold->work_is_cancelled= false;
+}
+
+enum decision_moment{
+  TH_KEY_UP = 0,
+  TH_OTHER_KEY_DOWN = 1,
+  TH_OTHER_KEY_UP = 2,
+  TH_TIMER_EVENT = 3,
+};
+
+static void decide_balanced(struct active_tap_hold * tap_hold, enum decision_moment event) {
+    switch(event) {
+    case TH_KEY_UP:
+      tap_hold->is_hold = 0;
+      tap_hold->is_decided = true;
+      break;
+    case TH_OTHER_KEY_UP:
+      tap_hold->is_hold = 1;
+      tap_hold->is_decided = true;
+      break;
+    case TH_TIMER_EVENT:
+      tap_hold->is_hold = 1;
+      tap_hold->is_decided = true;
+      break;
+    default: return;
+  }
+}
+
+static void decide_tap_preferred(struct active_tap_hold * tap_hold, enum decision_moment event) {
+    switch(event) {
+    case TH_KEY_UP:
+      tap_hold->is_hold = 0;
+      tap_hold->is_decided = true;
+      break;
+    case TH_TIMER_EVENT:
+      tap_hold->is_hold = 1;
+      tap_hold->is_decided = true;
+      break;
+    default: return;
+  }
+}
+
+static void decide_hold_preferred(struct active_tap_hold * tap_hold, enum decision_moment event) {
+    switch(event) {
+    case TH_KEY_UP: 
+      tap_hold->is_hold = 0;
+      tap_hold->is_decided = true;
+      break;
+    case TH_OTHER_KEY_DOWN:
+      tap_hold->is_hold = 1;
+      tap_hold->is_decided = true;
+      break;
+    case TH_TIMER_EVENT:
+      tap_hold->is_hold = 1;
+      tap_hold->is_decided = true;
+      break;
+    default: return;
+  }
+}
+
+
+void decide_tap_hold(struct active_tap_hold * tap_hold, enum decision_moment event)
+{
+  if (tap_hold->is_decided) {
+    return;
+  }
+
+  if(tap_hold != undecided_tap_hold) {
+    LOG_DBG("ERROR found undecided tap hold that is not the active tap hold");
+    return;
+  }
+
+  char* flavor = tap_hold->config->flavor;
+  if(strcmp(flavor, "balanced") == 0) {
+    decide_balanced(tap_hold, event);
+  } else if(strcmp(flavor, "tap-preferred") == 0) {
+    decide_tap_preferred(tap_hold, event);
+  } else if(strcmp(flavor, "hold-preferred") == 0) {
+    decide_hold_preferred(tap_hold, event);
+  }
+
+  if(!tap_hold->is_decided) {
+    return;
+  }
+
+  LOG_DBG("%d decided %s (%s event %d)", tap_hold->position, tap_hold->is_hold?"hold":"tap", flavor, event);
+
+  undecided_tap_hold = NULL;
+
+  struct zmk_behavior_binding *behavior;
+  if (tap_hold->is_hold) {
+    behavior = &tap_hold->config->behaviors->hold;
+  } else {
+    behavior = &tap_hold->config->behaviors->tap;
+  }
+  struct device *behavior_device = device_get_binding(behavior->behavior_dev);
+  behavior_keymap_binding_pressed(behavior_device,  tap_hold->position, behavior->param1, behavior->param2);
+  release_captured_positions();
+}
+
+/************************************************************  tap_hold_binding and key handlers */
+static int on_tap_hold_binding_pressed(struct device *dev, u32_t position, u32_t _, u32_t __)
+{
+  const struct behavior_tap_hold_config *cfg = dev->config_info;
+
+  if(undecided_tap_hold != NULL) {
+    LOG_DBG("ERROR another tap-hold behavior is undecided.");
+    // if this happens, make sure the behavior events occur AFTER other position events.
+    return 0;
+  }
+
+  struct active_tap_hold *tap_hold = store_tap_hold(position, cfg);
+  if (tap_hold == NULL) {
+    LOG_ERR("unable to store tap-hold info, did you press more than %d tap-holds?", ZMK_BHV_TAP_HOLD_MAX_HELD);
+    return 0;
+  }
+
+  LOG_DBG("%d new undecided tap_hold", position);
+  undecided_tap_hold = tap_hold;
+  k_delayed_work_submit(&tap_hold->work, cfg->tapping_term_ms());
+
+  //todo: once we get timing info for keypresses, start the timer relative to the original keypress
+  // don't forget to simulate a timer-event before the event after that time was handled.
+
+  return 0;
+}
+
+static int on_tap_hold_binding_released(struct device *dev, u32_t position, u32_t _, u32_t __)
+{
+  struct active_tap_hold *tap_hold = find_tap_hold(position);
+  if(tap_hold == NULL) {
+    LOG_ERR("ACTIVE_TAP_HOLD_CLEANED_UP_TOO_EARLY");
+    return 0;
+  }
+
+  int work_cancel_result = k_delayed_work_cancel(&tap_hold->work);
+  decide_tap_hold(tap_hold, TH_KEY_UP);
+
+  struct zmk_behavior_binding *behavior;
+  if (tap_hold->is_hold) {
+    behavior = &tap_hold->config->behaviors->hold;
+  } else {
+    behavior = &tap_hold->config->behaviors->tap;
+  }
+
+  struct device *behavior_device = device_get_binding(behavior->behavior_dev);
+  behavior_keymap_binding_released(behavior_device,  tap_hold->position, behavior->param1, behavior->param2);
+
+  if(work_cancel_result == -EINPROGRESS) {
+    // let the timer handler clean up
+    // if we'd clear now, the timer may call back for an uninitialized active_tap_hold.
+    LOG_DBG("%d tap-hold timer work in event queue", position);
+    tap_hold->work_is_cancelled = true;
+  } else {
+    LOG_DBG("%d cleaning up tap-hold", position);
+    clear_tap_hold(tap_hold);
+  }
+
+  return 0;
+}
+
+static const struct behavior_driver_api behavior_tap_hold_driver_api = {
+  .binding_pressed = on_tap_hold_binding_pressed,
+  .binding_released = on_tap_hold_binding_released,
+};
+
+int behavior_tap_hold_listener(const struct zmk_event_header *eh)
+{
+  if (!is_position_state_changed(eh)) {
+    return 0;
+  }
+  struct position_state_changed* ev = cast_position_state_changed(eh);
+  if(undecided_tap_hold == NULL) {
+    LOG_DBG("%d bubble (no undecided tap_hold active)", ev->position);
+    return 0;
+  }
+
+  if(undecided_tap_hold->position == ev->position) {
+    if(ev->state) {
+      LOG_ERR("this listener should be called before before the behavior listeners!");
+      return 0;
+    } else {
+      LOG_DBG("%d bubble undecided tap-hold keyrelease event", undecided_tap_hold->position);
+      return 0;
+    }
+  }
+
+  LOG_DBG("%d capturing %d %s event", undecided_tap_hold->position, ev->position, ev->state?"down":"up");
+
+  capture_position_event(ev);
+  if (ev->state) { 
+    decide_tap_hold(undecided_tap_hold, TH_OTHER_KEY_DOWN);
+  } else {
+    struct position_state_changed* captured_key_down = find_captured_keydown_event(ev->position); 
+    if(captured_key_down == NULL) {
+      // todo: allow key-up events for non-mod keys pressed before the TH was pressed.
+      // see scenario 3c/3d vs 3a/3b. 
+    } else {
+      decide_tap_hold(undecided_tap_hold, TH_OTHER_KEY_UP); 
+    }
+  }
+  return ZMK_EV_EVENT_CAPTURED;
+}
+
+ZMK_LISTENER(behavior_tap_hold, behavior_tap_hold_listener);
+ZMK_SUBSCRIPTION(behavior_tap_hold, position_state_changed);
+
+/************************************************************  TIMER FUNCTIONS */
+void behavior_tap_hold_timer_work_handler(struct k_work *item)
+{
+  struct active_tap_hold *tap_hold = CONTAINER_OF(item, struct active_tap_hold, work);
+  if(tap_hold->work_is_cancelled) {
+    clear_tap_hold(tap_hold);
+  } else {
+    decide_tap_hold(tap_hold, TH_TIMER_EVENT);
+  }
+}
+
+static int behavior_tap_hold_init(struct device *dev)
+{ 
+  static bool init_first_run = true;
+  if(init_first_run) {
+    for (int i = 0; i < ZMK_BHV_TAP_HOLD_MAX_HELD; i++) {
+        k_delayed_work_init(&active_tap_holds[i].work, behavior_tap_hold_timer_work_handler);
+        active_tap_holds[i].position = TH_POSITION_NOT_USED;
+      }
+  }
+  init_first_run = false;
+  return 0;
+}
+
+struct behavior_tap_hold_data {};
+static struct behavior_tap_hold_data behavior_tap_hold_data;
+
+/************************************************************ NODE CONFIG */
+#define _TRANSFORM_ENTRY(idx, node) \
+  { .behavior_dev = DT_LABEL(DT_INST_PHANDLE_BY_IDX(node, bindings, idx)), \
+    .param1 = COND_CODE_0(DT_INST_PHA_HAS_CELL_AT_IDX(node, bindings, idx, param1), (0), (DT_INST_PHA_BY_IDX(node, bindings, idx, param1))), \
+    .param2 = COND_CODE_0(DT_INST_PHA_HAS_CELL_AT_IDX(node, bindings, idx, param2), (0), (DT_INST_PHA_BY_IDX(node, bindings, idx, param2))), \
+  },
+
+#define KP_INST(n) \
+  static k_timeout_t behavior_tap_hold_config_##n##_gettime() { return K_MSEC(DT_INST_PROP(n, tapping_term_ms)); } \
+  static struct behavior_tap_hold_behaviors behavior_tap_hold_behaviors_##n = { \
+    .tap = _TRANSFORM_ENTRY(0, n) \
+    .hold = _TRANSFORM_ENTRY(1, n) \
+  }; \
+  static struct behavior_tap_hold_config behavior_tap_hold_config_##n = { \
+    .behaviors = &behavior_tap_hold_behaviors_##n, \
+    .tapping_term_ms = &behavior_tap_hold_config_##n##_gettime, \
+    .flavor = DT_INST_PROP(n, flavor), \
+  }; \
+  DEVICE_AND_API_INIT(behavior_tap_hold_##n, DT_INST_LABEL(n), behavior_tap_hold_init, \
+                      &behavior_tap_hold_data, \
+                      &behavior_tap_hold_config_##n, \
+                      APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT, \
+                      &behavior_tap_hold_driver_api);
+
+DT_INST_FOREACH_STATUS_OKAY(KP_INST)
+
+
+#endif
\ No newline at end of file
diff --git a/app/src/event_manager.c b/app/src/event_manager.c
index c405176f..22b92bfd 100644
--- a/app/src/event_manager.c
+++ b/app/src/event_manager.c
@@ -24,24 +24,24 @@ int zmk_event_manager_handle_from(struct zmk_event_header *event, u8_t start_ind
     u8_t len = __event_subscriptions_end - __event_subscriptions_start;
     for (int i = start_index; i < len; i++) {
         struct zmk_event_subscription *ev_sub = __event_subscriptions_start + i;
-        if (ev_sub->event_type == event->event) {
-            ret = ev_sub->listener->callback(event);
-            if (ret < 0) {
-                LOG_DBG("Listener returned an error: %d", ret);
+        if (ev_sub->event_type != event->event) {
+            continue;
+        }
+        ret = ev_sub->listener->callback(event);
+        if (ret < 0) {
+            LOG_DBG("Listener returned an error: %d", ret);
+            goto release;
+        } 
+        switch (ret) {
+            case ZMK_EV_EVENT_HANDLED:
+                LOG_DBG("Listener handled the event");
+                ret = 0;
                 goto release;
-            } else if (ret > 0) {
-                switch (ret) {
-                    case ZMK_EV_EVENT_HANDLED:
-                        LOG_DBG("Listener handled the event");
-                        ret = 0;
-                        goto release;
-                    case ZMK_EV_EVENT_CAPTURED:
-                        LOG_DBG("Listener captured the event");
-                        event->last_listener_index = i;
-                        // Listeners are expected to free events they capture
-                        return 0;
-                }
-            }
+            case ZMK_EV_EVENT_CAPTURED:
+                LOG_DBG("Listener captured the event");
+                event->last_listener_index = i;
+                // Listeners are expected to free events they capture
+                return 0;
         }
     }
 
@@ -55,6 +55,22 @@ int zmk_event_manager_raise(struct zmk_event_header *event)
     return zmk_event_manager_handle_from(event, 0);
 }
 
+int zmk_event_manager_raise_at(struct zmk_event_header *event, const struct zmk_listener *listener)
+{
+    u8_t len = __event_subscriptions_end - __event_subscriptions_start;
+    for (int i = 0; i < len; i++) {
+        struct zmk_event_subscription *ev_sub = __event_subscriptions_start + i;
+
+        if (ev_sub->event_type == event->event && ev_sub->listener == listener) {
+            return zmk_event_manager_handle_from(event, i+1);
+        }
+    }
+
+    LOG_WRN("Unable to find where to raise this after event");
+
+    return -EINVAL;
+} 
+
 int zmk_event_manager_raise_after(struct zmk_event_header *event, const struct zmk_listener *listener)
 {
     u8_t len = __event_subscriptions_end - __event_subscriptions_start;
@@ -74,4 +90,10 @@ int zmk_event_manager_raise_after(struct zmk_event_header *event, const struct z
 int zmk_event_manager_release(struct zmk_event_header *event)
 {
     return zmk_event_manager_handle_from(event, event->last_listener_index + 1);
+}
+
+
+int zmk_event_manager_release_again(struct zmk_event_header *event)
+{
+    return zmk_event_manager_handle_from(event, event->last_listener_index);
 }
\ No newline at end of file