Hi, thanks for the time and feedback! I'm glad you enjoyed the game overall!
The first version was actually FIFO, and I decided to change. I guess both FIFO and FILO lead to frustration, making me think there should be an extra verb you could do, like a second button to place the second on the line? I still don't have the answer. Many of the complaints talk about the lack of agency the core mechanic brings to a strategy game, which is usually not great. Thanks a lot for pointing that out! If I keep working on the game this will probably be the first aspect to try stuff and playtest.