Format:
triangle (int_x1, int_y1, int x2, int_y2, int_x3, int_y3, int_colour);
Draw triangle specified by the coordinates of its three defining points. If any part of the triangle falls outside of the screen boundaries, only the visible remainder is drawn.
If the colour is specified as negative number, only the outline of the triangle will be drawn, otherwise if the colour is a positive number, the triangle will be solid.
The function has no effect in the console or on text-only displays.