bop it or Simon games widely available playing intense console games, tetris etc...
Tetris is good in the sense that it can get very chaotic very quickly and as such is a good test of reaction times and the ability to make instant decisions. It will also highlight any tendency to panic and make a wrong move.
However, I would perservere with the Kris Mason download. I personally believe that there is no comparison to the test scenario where coloured circles are appearing randomly all over the screen. Furthermore, Tetris in my opinion is comparatively not as beneficial in this context in that all the blocks are originating in a fixed area of the screen and you do not have as many buttons to manipulate.
The perceived limitation with the download is that it is just a visual stimulus for practice. There is no feedback on your performance. Secondly, there is no provision for emulating the second part of the test where the speed of the test is controlled by your reactions purely because the download does not seem to be designed to be interactive.
I would like to stress that I have been nowhere near a DTG test in real life but I have no reason to doubt the excellent advice offered on these pages and other threads on this forum. I would forget Google and just do a search on this site for DTG test.
I would like to add that playing Tetris can be very time-consuming and I am sure the time could be better invested in other areas of preparation. The choice is yours.