2 weeks - it was also the first thing I ever programmed.
It was on my older brother’s TI-83 graphing calculator. I borrowed it and looked at the source of another game, and eventually made my own. It was a text RPG of sorts… basically you were a guy fighting in a tournament, you beat up progressively more and more difficult guys until you get to battle guess who, “Electric Eli.” Each person’s name was some sort of alliteration, if I recall. There was also training to increase your stats and all that.
In the end, though, it was just a typical stats-based text game. You had random chances to hit depending on where you chose to aim, you could strategically dodge, etc. In college I later made a game like it in Assembly. Also, the first version of the game was done in like 2 weeks, but I worked on it for months.
The key thing is that your first game should be simple in terms of programming, and then you’ll be fine. Having an example game to look at helps too.