public void Tick()
        {
            a = a++;
            screen.Clear(0);
            //top-left
            float x1 = -1, y1 = 1.0f;
            float rx1 = (float)(x1 * Math.Cos(a + 180) - y1 * Math.Sin(a + 180));
            float ry1 = (float)(x1 * Math.Sin(a + 180) + y1 * Math.Cos(a+ 180));

            //bot left
            float x2 = -1, y2 = -1;
            float rx2 = (float)(x2 * Math.Cos(a + 270) - y2 * Math.Sin(a + 270));
            float ry2 = (float)(x2 * Math.Sin(a + 270) + y2 * Math.Cos(a + 270));

            //bot right
            float x3 = 1.0f, y3 = -1;
            float rx3 = (float)(x3 * Math.Cos(a) - y3 * Math.Sin(a));
            float ry3 = (float)(x3 * Math.Sin(a) + y3 * Math.Cos(a));

            //top right
            float x4 = 1.0f, y4 = 1.0f;
            float rx4 = (float)(x4 * Math.Cos(a + 90) - y4 * Math.Sin(a + 90));
            float ry4 = (float)(x4 * Math.Sin(a + 90) + y4 * Math.Cos(a + 90));

            screen.Line(TX(x1), TY(y1), TX(x2), TY(y2), 0x0000ff);
            screen.Line(TX(x2), TY(y2), TX(x3), TY(x3), 0x00ff00);
            screen.Line(TX(x3), TY(y3), TX(x4), TY(x4), 0xff0000);
            screen.Line(TX(x4), TY(y4), TX(x1), TY(x1), 0xffffff);

            /*
            screen.Line(220, 100, 420, 100, 0x0000ff);
            screen.Line(220, 100, 220, 300, 0x00ff00);
            screen.Line(420, 100, 420, 300, 0xff0000);
            screen.Line(220, 300, 420, 300, 0xffffff);
            */

            screen.Print("hello world", 2, 2, 0xffffff);
            }

        public static int CreateColor(int red, int green, int blue)
         {
            return (red << 16) + (green << 8) + blue;
        }

        public int TY(float y) {
            y = y * -1;
            y = y + 2;
            y = (400 / 4) * y;
            return (int)y;
        }

        public int TX(float x){
            x = x + 2;
            x = (640 / 4 )* x / 1.6f;
            return (int)x;
        }