==========
   $90
==========
Probably the Intro-Scene-Counter?

- Set in Init to $10

- Used in IntroSpriteDeactivator (has to be #$01)
- Used in the Mainloop (JSR)

==========
   $E7
==========

- Used in IntroSpriteDeactivator (must not be #$00)

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==========
   $1026
==========

- Used in IntroSpriteDeactivator (has to be #$00)