An evening? Depends on what you mean by "Tetris" and the target quality. I did a two player Tetris-over-network for a class once (the opponent gets an additional garbled line when you clear multiple lines). It's easy, which is part of the problem: with enough expertise, it can become boring, you don't learn as much new stuff, it becomes more like laying bricks, not designing intricate machines or learning the principles of their operation.

An estimate that I heard on multiple occasions, disbelieved, and then witnessed come true, is that it takes about 4 years of hands-on experience for an enthusiastic smart adult to conquer the learning curve and as a result lose enthusiasm for software development in the abstract (so that you'd need something special about the purpose of the activity, not just the activity itself). I don't know about the probability of this happening, but the timescale seems about right.