Sorry about that. When you spend time with Casey, her mood increases by +2; when you eat with Casey, her mood increases by +1. But if you don't eat the whole day, her mood drops by -3. The fastest way to level up is to eat once and spend time with her twice each day.
Why even bother with the sandbox? Seriously, not only does nothing ever happen due to it, but it wastes both player and developer time. What about the game is improved by the sandbox? The answer is literally nothing. This is the most bare-bones, tedious sandbox I've seen in years, this game is like a relic from 2015, not a new game from 2025.