Drag the points of the lines. Don't move two points together, or else they will merge together. To get rid of them, click the flag again. Press space to show the list of equation in how the intersection of two infinite lines is found, and press space again to close.
My own legit intersection-line-detector, with the help of slopes, finding points between lines, and system of equations. There are many comments inside so you don't get confused.
