collision

.proc ChkTouchGeneric
; (abs(a.x - b.x) * 2 < (a.width + b.width))
  lda TouchWidthA
  add TouchWidthB
  sta TouchTemp

  lda TouchLeftA
  sub TouchLeftB
  bpl :+
  eor #255
  add #1
: asl
  cmp TouchTemp
  bcs No

; (abs(a.y - b.y) * 2 < (a.height + b.height))
  lda TouchHeightA
  add TouchHeightB
  sta TouchTemp

  lda TouchTopA
  sub TouchTopB
  bpl :+
  eor #255
  add #1
: asl
  cmp TouchTemp
  bcs No
  sec
  rts
No:
  clc
  rts
.endproc