setscreen ("graphics:400;600, nobuttonbar, offscreenonly")

const cx := maxx div 2
const cy := maxy div 2
var angle, slope : real := 0
var chars : array char of boolean
var mouseX, mouseY, mouseButton, shotX, shotY : int := 0

% Changeable variables
var shotSize := 10
var cannonLength := 80
var cannonWidth := 10

% Checks the mouse's boundaries
procedure mouseBounds
    % If the mouse's  x position is outside of the window then the mouseX value is still inside
    if mouseX < 0 then
        mouseX := 0
    elsif mouseX > maxx then
        mouseX := maxx
    end if
    % If the mouse's  y position is outside of the window then the mouseY value is still inside
    if mouseY < 0 then
        mouseY := 0
    elsif mouseY > maxy then
        mouseY := maxy
    end if
end mouseBounds
% Limits the angle (and slope value) of the cannon
procedure limitAngleSlope (minAngle, maxAngle : int)
    % If the angle is greater than the max angle it becomes the max angle and the slope value is equal to the maxangle
    if angle > maxAngle then
        angle := maxAngle
        slope := tand (angle)
        % If the angle is less than the min angle it becomes the max angle and the slope value is equal to the minangle
    elsif angle < minAngle and mouseX >= 200 then
        angle := minAngle
        slope := tand (angle)
    elsif angle < minAngle and mouseX < 200 then
        angle := maxAngle
        slope := tand (angle)
    end if
end limitAngleSlope

% Creates a picture of a cannon
var picCannon, rotateCannon : int
drawfillbox (0, 0, maxx, maxy, black)
drawfillbox (cannonLength - cannonWidth, 0, cannonLength + cannonWidth, cannonLength, grey)
picCannon := Pic.New (0, 0, cannonLength * 2, cannonLength)

% Clears the screen
cls

% Main Loop
loop
    Input.KeyDown (chars)
    View.Update

    % Draws background
    drawfillbox (0, 0, maxx, maxy, black)

    % Finds the coordinates of the mouse
    Mouse.Where (mouseX, mouseY, mouseButton)
    % Checks the mouse boundaries
    mouseBounds
    % If the mouse's x position is not equal to the center of the screen
    if mouseX not= cx then
        % Then calculate the slope and the angle
        slope := mouseY / (mouseX - cx)
        angle := arctand (slope)
    else
        % Else the angle is 90 (and slope is undefined)
        angle := 90
    end if
    % Changes the negative angles to the correct angle
    if angle < 0 then
        angle := angle + 180
    end if
    % Limits the angle (and slope value) of the cannon if it is less than 10 degrees or greater than 170 degrees
    limitAngleSlope (10, 170)

    % Rotates the barrel of the cannon according to the angle
    rotateCannon := Pic.Rotate (picCannon, round (angle) - 90, cannonLength, 0)
    % Draws the barrel of the cannon according to the rotation
    Pic.Draw (rotateCannon, cx - cannonLength, 0, picMerge)
    Pic.Free (rotateCannon)
    % Draws the cannon circle
    drawfilloval (cx, 0, cannonLength div 2, cannonLength div 2, grey)
    drawoval (cx, 0, cannonLength div 2 - 5, cannonLength div 2 - 5, white)
    drawoval (cx, 0, cannonLength div 2, cannonLength div 2, white)
    % Draws the red line
    drawline (0, 30, maxx, 30, red)

    % Calculates the coordinates of the shot
    shotX := round (cannonLength * cosd (angle))
    shotY := round (cannonLength * sind (angle))
    % If the left button is pressed then draw the shot
    if mouseButton = 1 then
        % Draws the shot
        drawoval (shotX + cx, shotY, shotSize, shotSize, white)
        drawoval (shotX + cx, shotY, shotSize - 5, shotSize - 5, white)
    end if

    % Quits when the user presses q
    if chars ('q') then
        Pic.Free (picCannon)
        delay (200)
        exit
    end if
end loop

View.Set ("offscreenonly")
var x, y, dx, dy : array - 5 .. 5 of int
var mx, my, b, t : int

for i : -5 .. 5
    x (i) := 200
    y (i) := 200
    dx (i) := 200
    dy (i) := 200
end for

loop

    Mouse.Where (mx, my, b)

    for i : -5 .. 5
        Draw.Line (dx (i), dy (i), x (i), y (i), 7)
    end for

    if b = 1 then
        if mx > 200 then
            t := round (arctand ((my - 200) / (mx - 200)))
        elsif mx < 200 then
            t := round (arctand ((my - 200) / (mx - 200))) - 180
        end if
        for i : -5 .. 5
            dx (i) := 200 + round (i * cosd (t - 90))
            dy (i) := 200 + round (i * sind (t - 90))
            x (i) := dx (i) + round (100 * cosd (t))
            y (i) := dy (i) + round (100 * sind (t))
        end for
    end if

    View.UpdateArea (0, 0, maxx, maxy)
    delay (20)
    cls

end loop