>Dragan,
>
>>Finished level 15 at 1,631,244 after no less than ten warnings. The last moves take just too long.
>
>It hung on me last night the next time at level 10 finish time. So I'm not sure ever get much beyond that.

My machine is slower - about 1.6GHz, so I notice the slowdown few moves to the end. It actually depends on how soon does it find an existing intersection. If it's somewhere high on the list, it may still be fast.

>If Vertex E was moved below and between C D, line 5 would have to be intersect checked against 1,2,3,4, afterwards the crossing list would look like:
>
>1 - null
>2 - 3
>3 - 2
>4 - 5
>5 - 3,4

Yeah, that was the idea. Or a global triangular matrix: 1-2, 1-3, ... 1-n; 2-3, 2-4, ... 2-n etc. And then for any particular move, check the lines moved against all other lines.