' ROTOZOOM.BAS

SCREEN 13

DEF SEG = &HA000

angle! = 0
zoom! = 1
fps! = 1

offx! = 0
offy! = 0


frames% = 0
lastt& = TIMER



DO WHILE INKEY$ = ""

    ptr& = 0


    dx! = zoom! * COS(angle!)
    dy! = zoom! * SIN(angle!)

    spx! = offx! - (-dy! * 100 + dx! * 150)
    spy! = offy! - (dx! * 100 + dy! * 150)

    FOR y% = 0 TO 199

        px! = spx!
        py! = spy!

        spx! = spx! - dy!
        spy! = spy! + dx!

        FOR x% = 0 TO 319
            POKE ptr&, px! XOR py!
            px! = px! + dx!
            py! = py! + dy!
            ptr& = ptr& + 1
        NEXT x%
    NEXT y%

    frames% = frames% + 1
    thist& = TIMER

    IF thist& <> lastt& THEN
        fps! = frames% / (thist& - lastt&)
        IF fps! = 0 THEN fps! = .1
        frames% = 0
        lastt& = thist&
    END IF

    angle! = angle! + (.7 / fps!)
    zoom! = 1.4 + COS(angle! / 3.3)
    offx! = offx! + 60 / fps!
    offy! = offy! + 80 / fps!

    WAIT &H3DA, 8

LOOP