diff --git a/aqt/__init__.py b/aqt/__init__.py
index 1d6df5930..4bd09abad 100644
--- a/aqt/__init__.py
+++ b/aqt/__init__.py
@@ -10,7 +10,9 @@ import tempfile
 import builtins
 import locale
 import gettext
+from typing import Optional
 
+from aqt.main import AnkiQt
 from aqt.qt import *
 import anki.lang
 from anki.consts import HELP_SITE
@@ -24,7 +26,7 @@ appDonate="http://ankisrs.net/support/"
 appShared="https://ankiweb.net/shared/"
 appUpdate="https://ankiweb.net/update/desktop"
 appHelpSite=HELP_SITE
-mw = None # set on init
+mw: Optional[AnkiQt] = None # set on init
 
 moduleDir = os.path.split(os.path.dirname(os.path.abspath(__file__)))[0]
 
diff --git a/aqt/addcards.py b/aqt/addcards.py
index b97b559a4..bd00e78bb 100644
--- a/aqt/addcards.py
+++ b/aqt/addcards.py
@@ -1,8 +1,10 @@
 # Copyright: Ankitects Pty Ltd and contributors
 # -*- coding: utf-8 -*-
 # License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
-from anki.lang import _
+from typing import List
 
+from anki.lang import _
+from aqt import AnkiQt
 from aqt.qt import *
 import aqt.forms
 from aqt.utils import saveGeom, restoreGeom, showWarning, askUser, shortcut, \
@@ -14,7 +16,7 @@ import aqt.editor, aqt.modelchooser, aqt.deckchooser
 
 class AddCards(QDialog):
 
-    def __init__(self, mw):
+    def __init__(self, mw: AnkiQt):
         QDialog.__init__(self, None, Qt.Window)
         mw.setupDialogGC(self)
         self.mw = mw
@@ -27,7 +29,7 @@ class AddCards(QDialog):
         self.setupEditor()
         self.setupButtons()
         self.onReset()
-        self.history = []
+        self.history: List[int] = []
         self.previousNote = None
         restoreGeom(self, "add")
         addHook('reset', self.onReset)
diff --git a/aqt/browser.py b/aqt/browser.py
index ee782a805..39d10b630 100644
--- a/aqt/browser.py
+++ b/aqt/browser.py
@@ -11,6 +11,7 @@ from operator import  itemgetter
 from anki.lang import ngettext
 import json
 
+from aqt import AnkiQt
 from aqt.qt import *
 import anki
 import aqt.forms
@@ -383,7 +384,7 @@ class StatusDelegate(QItemDelegate):
 
 class Browser(QMainWindow):
 
-    def __init__(self, mw):
+    def __init__(self, mw: AnkiQt):
         QMainWindow.__init__(self, None, Qt.Window)
         self.mw = mw
         self.col = self.mw.col
diff --git a/aqt/editor.py b/aqt/editor.py
index 9283779ca..c0c3f2041 100644
--- a/aqt/editor.py
+++ b/aqt/editor.py
@@ -11,6 +11,7 @@ import unicodedata
 import json
 
 from anki.lang import _
+from aqt import AnkiQt
 from aqt.qt import *
 from anki.utils import isWin, namedtmp, stripHTMLMedia, \
     checksum
@@ -40,7 +41,7 @@ html { background: %s; }
 
 # caller is responsible for resetting note on reset
 class Editor:
-    def __init__(self, mw, widget, parentWindow, addMode=False):
+    def __init__(self, mw: AnkiQt, widget, parentWindow, addMode=False):
         self.mw = mw
         self.widget = widget
         self.parentWindow = parentWindow
diff --git a/aqt/main.py b/aqt/main.py
index 9244ee33c..616dd4623 100644
--- a/aqt/main.py
+++ b/aqt/main.py
@@ -10,8 +10,9 @@ import time
 import faulthandler
 import platform
 from threading import Thread
-
+from typing import Optional
 from send2trash import send2trash
+from anki.collection import _Collection
 from aqt.qt import *
 from anki.storage import Collection
 from anki.utils import  isWin, isMac, intTime, splitFields, ids2str, \
@@ -36,6 +37,7 @@ class AnkiQt(QMainWindow):
         QMainWindow.__init__(self)
         self.state = "startup"
         self.opts = opts
+        self.col: Optional[_Collection] = None
         aqt.mw = self
         self.app = app
         self.pm = profileManager
diff --git a/aqt/reviewer.py b/aqt/reviewer.py
index 03b228310..c47bff4e0 100644
--- a/aqt/reviewer.py
+++ b/aqt/reviewer.py
@@ -9,7 +9,11 @@ import unicodedata as ucd
 import html.parser
 import json
 
+from typing import List
+
+from anki.cards import Card
 from anki.lang import _, ngettext
+from aqt import AnkiQt
 from aqt.qt import *
 from anki.utils import stripHTML, bodyClass
 from anki.hooks import addHook, runHook, runFilter
@@ -23,13 +27,13 @@ import aqt
 class Reviewer:
     "Manage reviews.  Maintains a separate state."
 
-    def __init__(self, mw):
+    def __init__(self, mw: AnkiQt):
         self.mw = mw
         self.web = mw.web
         self.card = None
-        self.cardQueue = []
+        self.cardQueue: List[Card] = []
         self.hadCardQueue = False
-        self._answeredIds = []
+        self._answeredIds: List[int] = []
         self._recordedAudio = None
         self.typeCorrect = None # web init happens before this is set
         self.state = None