Huh? What?

I was reading my friend's letter...

Коля уже дома. Он пришел из армии 21 июня.
Сделал свой тетрис. Сам потихоньку постигает науку программирования.

"Сделал свой тетрис." ??

I thought Tetris was a software game... :)

Li'l help? Спасибо!

It is, but the letter still makes sense.
“ Kolya is already at home. He came from the army on June 21.
He made (wrote) his own tetris. He is slowly learning the science of programming.”
In other words, he has learned enough about programming to write a simple (-ish!) game like Tetris.

known already since 1984 when it was still CCCP..https://en.wikipedia.org/wiki/Tetris

"I see!" said the blind man.

Thanks, guys!