love2d绘制一个跟随鼠标移动的圆

今天学习了love2d游戏开发引擎制作一个可以跟随鼠标移动的圆，并且通过勾股定理计算出圆到鼠标的distance。

there is code

function love.load()
    circle = {};
    circle.x = 200;
    circle.y = 300;
    circle.radius = 25;
    circle.speed = 200;
end

function getDistance(x1,y1,x2,y2)
    local horizantal_distance = x1 - x2;
    local vertical_distance = y1 - y2;

    local a = horizantal_distance ^ 2;
    local b = vertical_distance ^ 2;
    local c = a + b;
    local distance = math.sqrt(c);
    return distance;
end

function love.update(dt)
    mouse_x,mouse_y = love.mouse.getPosition();
    angle = math.atan2(mouse_y-circle.y,mouse_x-circle.x);
    sin = math.sin(angle);
    cos = math.cos(angle);

    local distance = getDistance(mouse_x,mouse_y,circle.x,circle.y);
    if distance<300 then
        circle.x = circle.x + circle.speed * cos * dt;
        circle.y = circle.y + circle.speed * sin * dt;
    end

end

function love.draw()
    love.graphics.circle("line",circle.x,circle.y,circle.radius)
    love.graphics.print("The angle: "..angle,20,10);

    love.graphics.line(circle.x,circle.y,mouse_x,mouse_y);
    love.graphics.line(circle.x,circle.y,mouse_x,circle.y)
    love.graphics.line(mouse_x,mouse_y,mouse_x,circle.y)
    local distance = getDistance(mouse_x,mouse_y,circle.x,circle.y);
    love.graphics.circle("line",circle.x,circle.y,distance);
end