Why did Britain and Russia become involved in a "Great Game" in Central Asia?

The Great Game was an intense and fierce rivalry between the Russia and Great Britain that played out in the 19th century.

Russia began a great expansion effort in the Central Asia as historians say in the bid to make the one the largest empires in the human history land wise. They started moving in the direction of India which was the British jewel. The Great Britain in response to the Russian expansion started created a "buffer" zone through conquering or influencing the states around India.