Man thanks for the amazing comment, also since you are interested in the design I used iterative approach. I first started with basic linear progression but that didn't really fit the game I wanted something that become more chaotic as you progress. So I added insane upgrades at the end like madness that require a lot of money, I made sure you didn't get the upgrade too fast to ensure the player didn't get exhausted or overrun by everything that is going on. I tweaked it till on average I had 1 minute of madness which felt the most balanced, though there is probably some people out there that are better at my own game. Play testing was the largest part of my development since the majority of mechanics were easy to implement and my art skills are limited so I also didn't have to use a lot of my time there.
If there is anything I can improve also let me know I feel like the first few minutes are slow, though I'm not sure how I would improve that without breaking my current design.