I feel the salary of 140 is too high and consequently the feeling of progress is too slow (i.e some days without any upgrade with 6 workers did feel bad). Would suggest decrease it to 120 for example
Thank you so much for your feedback, we really appreciate it. We were aiming for a learning process meaning you play the game many times and each time you learn something new and improve. I feel that reducing the salary might be really good for first play throughs but after a few play throughs it becomes too easy. From an experience like yours a player can learn to focus more on upgrades and wait with hiring more miners. Anyways, thank you so much for the comment.