diff --git a/app/__init__.py b/app/__init__.py
new file mode 100644
index 0000000..47f814f
--- /dev/null
+++ b/app/__init__.py
@@ -0,0 +1,5 @@
+# For relative imports to work in Python 3.6
+import os
+import sys
+
+sys.path.append(os.path.dirname(os.path.realpath(__file__)))
diff --git a/app/hid.py b/app/hid.py
new file mode 100644
index 0000000..440f0f8
--- /dev/null
+++ b/app/hid.py
@@ -0,0 +1,7 @@
+def send(hid_path, control_keys, hid_keycode):
+    with open(hid_path, 'wb+') as hid_handle:
+        buf = [0] * 8
+        buf[0] = control_keys
+        buf[2] = hid_keycode
+        hid_handle.write(bytearray(buf))
+        hid_handle.write(bytearray([0] * 8))
diff --git a/app/js_to_hid.py b/app/js_to_hid.py
new file mode 100644
index 0000000..37aca14
--- /dev/null
+++ b/app/js_to_hid.py
@@ -0,0 +1,165 @@
+import dataclasses
+
+
+class Error(Exception):
+    pass
+
+
+class UnrecognizedKeyCodeError(Error):
+    pass
+
+
+@dataclasses.dataclass
+class JavaScriptKeyEvent:
+    meta_modifier: bool
+    alt_modifier: bool
+    shift_modifier: bool
+    ctrl_modifier: bool
+    key: str
+    key_code: int
+
+
+# JS keycodes source: https://github.com/wesbos/keycodes
+# HID keycodes source: https://gist.github.com/MightyPork/6da26e382a7ad91b5496ee55fdc73db2
+
+# TODO: For simplicity, we map all modifiers keys to the left key, but we could
+# support distinct keys for left and right if we check the location parameter
+# from the JavaScript message.
+_JS_TO_HID_KEYCODES = {
+    3: 0x48,  # Pause / Break
+    8: 0x2a,  # Backspace / Delete
+    9: 0x2b,  # Tab
+    12: 0x53,  # Clear
+    13: 0x28,  # Enter
+    16: 0xe1,  # Shift (Left)
+    17: 0xe0,  # Ctrl (left)
+    18: 0xe1,  # Alt (left)
+    19: 0x48,  # Pause / Break
+    20: 0x39,  # Caps Lock
+    21: 0x90,  # Hangeul
+    25: 0x91,  # Hanja
+    27: 0x29,  # Escape
+    32: 0x2c,  # Spacebar
+    33: 0x4b,  # Page Up
+    34: 0x4e,  # Page Down
+    35: 0x4d,  # End
+    36: 0x4a,  # Home
+    37: 0x50,  # Left Arrow
+    38: 0x52,  # Up Arrow
+    39: 0x4f,  # Right Arrow
+    40: 0x51,  # Down Arrow
+    41: 0x77,  # Select
+    43: 0x74,  # Execute
+    44: 0x46,  # Print Screen
+    45: 0x49,  # Insert
+    46: 0x4c,  # Delete
+    47: 0x75,  # Help
+    48: 0x27,  # 0
+    49: 0x1e,  # 1
+    50: 0x1f,  # 2
+    51: 0x20,  # 3
+    52: 0x21,  # 4
+    53: 0x22,  # 5
+    54: 0x23,  # 6
+    55: 0x24,  # 7
+    56: 0x25,  # 8
+    57: 0x26,  # 9
+    59: 0x33,  # Semicolon
+    60: 0xc5,  # <
+    61: 0x2e,  # Equal sign
+    65: 0x04,  # a
+    66: 0x05,  # b
+    67: 0x06,  # c
+    68: 0x07,  # d
+    69: 0x08,  # e
+    70: 0x09,  # f
+    71: 0x0a,  # g
+    72: 0x0b,  # h
+    73: 0x0c,  # i
+    74: 0x0d,  # j
+    75: 0x0e,  # k
+    76: 0x0f,  # l
+    77: 0x10,  # m
+    78: 0x11,  # n
+    79: 0x12,  # o
+    80: 0x13,  # p
+    81: 0x14,  # q
+    82: 0x15,  # r
+    83: 0x16,  # s
+    84: 0x17,  # t
+    85: 0x18,  # u
+    86: 0x19,  # v
+    87: 0x1a,  # w
+    88: 0x1b,  # x
+    89: 0x1c,  # y
+    90: 0x1d,  # z
+    91: 0xe3,  # Windows key / Meta Key (Left)
+    96: 0x62,  # Numpad 0
+    97: 0x59,  # Numpad 1
+    98: 0x5a,  # Numpad 2
+    99: 0x5b,  # Numpad 3
+    100: 0x5c,  # Numpad 4
+    101: 0x5d,  # Numpad 5
+    102: 0x5e,  # Numpad 6
+    103: 0x5f,  # Numpad 7
+    104: 0x60,  # Numpad 8
+    105: 0x61,  # Numpad 9
+    112: 0x3a,  # F1
+    113: 0x3b,  # F2
+    114: 0x3c,  # F3
+    115: 0x3d,  # F4
+    116: 0x3e,  # F5
+    117: 0x3f,  # F6
+    118: 0x40,  # F7
+    119: 0x41,  # F8
+    120: 0x42,  # F9
+    121: 0x43,  # F10
+    122: 0x44,  # F11
+    123: 0x45,  # F12
+    124: 0x68,  # F13
+    125: 0x69,  # F14
+    126: 0x6a,  # F15
+    127: 0x6b,  # F16
+    128: 0x6c,  # F17
+    129: 0x6d,  # F18
+    130: 0x6e,  # F19
+    131: 0x6f,  # F20
+    132: 0x70,  # F21
+    133: 0x71,  # F22
+    134: 0x72,  # F23
+    144: 0x53,  # Num Lock
+    145: 0x47,  # Scroll Lock
+    161: 0x1e,  # !
+    163: 0x32,  # Hash
+    173: 0x2d,  # Minus
+    179: 0xe8,  # Media play/pause
+    168: 0xfa,  # Refresh
+    186: 0x33,  # Semicolon
+    187: 0x2e,  # Equal sign
+    188: 0x36,  # Comma
+    189: 0x2d,  # Minus sign
+    190: 0x37,  # Period
+    191: 0x38,  # Forward slash
+    192: 0x35,  # Accent grave
+    219: 0x2f,  # Left bracket ([, {])
+    220: 0x31,  # Back slash
+    221: 0x30,  # Right bracket (], })
+    222: 0x34,  # Single quote
+    223: 0x35,  # Accent grave (`)
+}
+
+
+def convert(js_key_event):
+    control_chars = 0
+    for i, pressed in enumerate([
+            js_key_event.ctrl_modifier, js_key_event.shift_modifier,
+            js_key_event.alt_modifier, js_key_event.meta_modifier
+    ]):
+        if pressed:
+            control_chars |= 1 << i
+    try:
+        return control_chars, _JS_TO_HID_KEYCODES[js_key_event.key_code]
+    except KeyError:
+        raise UnrecognizedKeyCodeError(
+            'Unrecognized key code %s (%d)' %
+            (js_key_event.key, js_key_event.key_code))