Congrats on finishing a game for the jam! It's an interesting idea to have everything either cost or reward time, especially even the shooting. The upgrade system adds interest to the game, but I wasn't quite able to understand the UI (when I had "ticks" and how many, and what the buttons on the bottom of the screen did).
Nice job overall!
Thanks for the nice comment. The "ticks" are displayed in the upgrade menu, above the menu itself.