NES collision

.proc ChkTouchGeneric
  jsr :+
  swapa TouchLeftA,   TouchLeftB
  swapa TouchTopA,    TouchTopB
  swapa TouchWidthA,  TouchWidthB
  swapa TouchHeightA, TouchHeightB
  jsr :+
  clc ; no collision
  rts
: lda TouchLeftB
  add TouchWidthB
  sta TouchRight
  lda TouchTopB
  add TouchHeightB
  sta TouchBottom

  lda TouchLeftA
  cmp TouchLeftB
  bcc :+

  lda TouchLeftA
  cmp TouchRight
  bcs :+

  lda TouchTopA
  cmp TouchTopB
  bcc :+

  lda TouchTopA
  cmp TouchBottom
  bcs :+
  pla
  pla
  sec ; collision detected
: rts
.endproc