Amphitheatre CF strats and a few other refinements

[blkerby]

The existing 2->3 strat seemed not right to me: the heat/acid frames seemed very loose, and I couldn't see any benefit from the reset fall speed or wall jump options; it's possible I'm missing something though.

Normally traversing the room right-to-left needs at least 5 tanks with either Varia or Gravity. With a CF in the safe place at the bottom of the room, this can be reduced to 4 tanks with Varia or 3 tanks with Gravity (very tight). If weapons are available to kill the bottom-left Pirate, 3 tanks with Varia also becomes possible.

Videos:

• Crystal Flash in safe spot with Varia (4 tanks): https://videos.maprando.com/video/7404
• Crystal Flash in safe spot with Gravity (3 tanks): https://videos.maprando.com/video/7407
• Kill Pirates and CF with Varia (3 tanks, Charge+Plasma): https://videos.maprando.com/video/7406
• Kill Pirates and CF with Varia (3 tanks, Supers): https://videos.maprando.com/video/7405