% /////////////////////
% // Michael Yazdani //
% /////////////////////
% // ICS 3U ///////////
% /////////////////////

setscreen ("graphics:700;700")

% VARIABLE ANS CONSTANT DECLARATIONS

var x, y : int
const inc := 5
const radius := 25
var chars : array char of boolean

% FORWARD DECLARATIONS
forward procedure moveleft


% PROCEDURES

procedure keydown       % determines what keys are being pressed
    Input.KeyDown (chars)
end keydown

procedure circle        % draws a circle at location x and y with radius "radius" then erases for next frame
    drawoval (x, y, radius, radius, 1)
    delay (16)
    drawoval (x, y, radius, radius, white)
end circle

body procedure moveleft         % sets x to x - inc, if x is less than radius, moveright is called
    loop
        keydown
        exit when chars (KEY_ESC)
        if chars (KEY_UP_ARROW) then
        y := y + inc
        end if
        if chars (KEY_DOWN_ARROW) then
        y := y - inc
        end if
        if chars (KEY_LEFT_ARROW) then
        x := x - inc
        end if
        if chars (KEY_RIGHT_ARROW) then
        x := x + inc
        end if
        if x > maxx - radius then
        x := x - inc
        end if
        if x < radius then
        x := x + inc
        end if
        if y > maxy - radius then
        y := y - inc
        end if
        if y < radius then
        y := y + inc
        end if
        circle
    end loop
end moveleft

% VARIABLE INITILIZATION

x := maxx div 2         % initializes x to center of output window
y := maxy div 2         % initializes y to center of output window

% MAIN PROGRAM

loop
    keydown
    exit when chars (KEY_ESC)   % exits main loop, terminates program
    if chars (KEY_LEFT_ARROW) or chars (KEY_RIGHT_ARROW) or chars (KEY_UP_ARROW) or chars (KEY_DOWN_ARROW) then
        moveleft
    end if
end loop

cls
put "Program Terminated."