Fix spelling and add some comments

Author: lulunac27a

app.py

@@ -42,7 +42,7 @@ def check_level_up(self):  # check if user has leveled up
             self.xp -= self.xp_required
             self.xp_required = round(
                 self.xp_required + self.xp_required * 1 / math.sqrt(self.level)
-            )
+            )  # increase XP required exponentially with slower growth at higher levels
             self.level += 1  # increase level
 
     def get_xp_required(self):  # get required XP to next level
@@ -107,7 +107,7 @@ def index():  # get index page template
     Return the index page containing a user.
     """
     user = User.query.first()  # get first user
-    return render_template("index.html", user=user)  # return index page template
+    return render_template("index.html", user=user)  # redirect to index page template
 
 
 @app.route("/add_xp", methods=["POST"])  # add XP from POST method
@@ -118,21 +118,21 @@ def add_xp():  # add XP
     user = User.query.first()  # get first user
     user.add_xp(float(request.form["amount"]))  # parse amount as float
     db.session.commit()  # commit database changes
-    return redirect(url_for("index"))  # return index page template
+    return redirect(url_for("index"))  # redirect to index page template
 
 
 def init_db():  # initialize database
     """
     Initialize the user database.
     """
     with app.app_context():
-        db.create_all()  # initialize database
+        db.create_all()  # create tables if they don't exist
         if User.query.count() == 0:  # if there is no user in database
             new_user = User(username="Player")  # add user with name 'Player'
             db.session.add(new_user)  # add new user to database
             db.session.commit()  # commit database changes
 
 
 if __name__ == "__main__":
-    init_db()
-    app.run(debug=True, port=8081)  # run the app at post 8081
+    init_db()  # initialize database
+    app.run(debug=True, port=8081)  # run the app at port 8081