Trax

from the Trax site:

Trax is a two player abstract strategy game of loops and lines. It can be played on any flat surface (no board). The square tiles have straights on one side and curves on the other.

The rules of TRAX are simple: place tiles adjacent to those already in play such that the colours of the tracks match. The objective is to get a loop or line of your colour while attempting to stop your opponent in their colour. What gives Trax its strategic depth is the forced play rule which allows (or even requires) multiple tiles to be played in a turn.