The tetris theme is an instrumental arrangement of a Russian folk tune called Korobeiniki. Here we play it out on guitar, twice. First time through we play it true to the original melody. The main melody is really quite short. It is played twice and then a little descending tune is played.

After that, the whole thing is played again, however, this time we add a couple of hammer on / pull off combinations, just to add a little something. Once you have the tune nailed, experiment with it yourself. Add bends, vibrato, slides etc to embellish it and make it your own.

Practicing strong melodies like this is a good approach for beginners. The more familiar you are with a melody, the easier it is to learn. Even if you don't know the tune, a strong melody can quickly be learned and remembered. The main reason such melodies are good for practice is that it's easier to tell if you are playing it right or wrong while practicing. This particular tune is a good one for learning to build speed. It is naturally a fast tune, but even when played slowly it is easy to recognise the melody.

When practicing, go as slow as you need to. Make sure your fingers learn the melody first at a slower pace, then work on building speed. Divide the melody into small chunks, for example, the first 10 notes. Work at those 10 notes until you have them nailed, then work on the next chunk of 10 notes (or whatever seems comfortable). Use your own sense of natural rhythm / melody to determine the size of each chunk. Don't bite off more than you can chew. If it means using chunks of 3 notes at a time, then that's fine. Different people will have different capacities here. The point is to work in your comfort zone, and then push out from it. The more you practice this way, the faster you will develop. Also, the faster you will learn the tune.