The battle intro slide ran at 4px/frame over 40 frames -- twice the
original speed -- and drew the pics in their normal palette instead of
as black silhouettes.
SlidePlayerAndEnemySilhouettesOnScreen scrolls SCX from $90 to 0 at
2px/frame (~72 frames) under the %11100100 silhouette palette, only
running SET_PAL_BATTLE once the pics land. Match that: introSlide starts
at 80 with a 2px/frame offset (80 frames over the full 160px width), and
picImage bakes both pics through PAL_BLACK while introSlide > 0, exactly
like the evolution movie (#279).
parity_battle_intro_chrome waited a hardcoded 45 frames for the slide to
land; bumped to 85 to cover the slower slide.