python code which isn't working for me

# if it matters, here's the screen code, but I think this works fine.

screen explore1:
    frame:
        xpadding 10
        ypadding 10
        xalign 1.0
        yalign 0

        vbox:

            text "Explore your cell."
            null height 10
            textbutton "Try to leave." action Jump("leavecell")
            textbutton "Examine yourself." action Jump("exself")
            textbutton "Examine the brick walls." action Jump("exwalls")


label start:
    $ knowname = False
    $ cellkey = False

    j "Ugh..."
    j "Wh... why am I here?!"
    j "I don't remember anything..."
    show screen explore1
    jump chooseaction

label exwalls:
        j "Hard stone... the bricks are very refined."
        j "What's this?!"
        j "One of them's loose!"
        $ cellkey = True
        j "There's a key here!"
        jump chooseaction

label exself:
        j "Who am I...?"
        j "I...  I can't remember..."
        j "Huh? There's something in my pocket..."
        j "A wallet!"
        j "My name... it's Jack McKen."
        j "At least I know that now..."
        $ knowname = True
        jump chooseaction

label leavecell:

        j "It's time to get out of here!"
        if cellkey:
            j "Let's just use this key..."
            j "There!"
            jump outofcell
        else:
            j "The bars won't budge. There's gotta be something here which'll help me."
            jump chooseaction
label outofcell:

        j "Now I'm out of there... where am I?"
        j "This place is a prison... what am I doing here...?"

label chooseaction:
        "Choose an action."
        jump chooseaction

return


I'm sorry, but an uncaught exception occurred.

While running game code:
  File "game/script.rpy", line 44, in script
  File "game/script.rpy", line 44, in python
NameError: name 'cellkey' is not defined

-- Full Traceback ------------------------------------------------------------

Full traceback:
  File "C:\Documents and Settings\Lillian\My Documents\Games\Renpy\renpy\execution.py", line 265, in run
  File "C:\Documents and Settings\Lillian\My Documents\Games\Renpy\renpy\ast.py", line 1374, in execute
  File "C:\Documents and Settings\Lillian\My Documents\Games\Renpy\renpy\python.py", line 1009, in py_eval
  File "game/script.rpy", line 44, in <module>
NameError: name 'cellkey' is not defined

Windows-XP-5.1.2600-SP3
Ren'Py 6.13.12.1728
A Ren'Py Game 0.0