CLS
SCREEN 12

x = 0
y = 0

DO WHILE 1 = 1
        k$ = INKEY$
        IF k$ = CHR$(0) + "H" THEN
                CLS
                y = y - 5
        ELSEIF k$ = CHR$(0) + "P" THEN
                CLS
                y = y + 5
        ELSEIF k$ = CHR$(0) + "M" THEN
                CLS
                x = x + 5
        ELSEIF k$ = CHR$(0) + "K" THEN
                CLS
                x = x - 5
        END IF

        LINE (10 + x, 20 + y)-(20 + x, 40 + y), 4, BF

LOOP