RANDOMISE
CLS
width := 80; height := 40
x := width / 2; y := height / 2
oldx := x; oldy := y

REPEAT
    PRINT TAB (x, y) "¥";
    direction := RND 4
    CASE direction OF
        WHEN 1
            x := (x + 1) MOD width
        WHEN 2
            x := (x + width - 1) MOD width
        WHEN 3
            y := (y + 1) MOD height
        WHEN 4
            y := (y + height - 1) MOD height
        OTHERWISE
            CLS
            PRINT "Unknown direction"
            END
    ENDCASE
    PRINT TAB (oldx, oldy); "><v^" (direction);
    oldx := x; oldy := y
UNTIL FALSE