I'm not sure I understand the starting minigame, could you add a tutorial ? Secondlyn, the volumes feel a bit off, aren't the values a little smaller than the visuals ? Lastly, you mentioned milking and breast growth in other comments.
When would you say that would be added ? How about weight gain ?
there is no tutorial for the starting minigame because the reward for figuring it out is getting triplets. if i told you the exact mechanics, the reward wouldn't mean anything
the volumes are scaled so that the belly stages are spaced equally between a flat belly and the largest belly I can achieve with my modeling program, with later stages being spaced a bit further. there is no IRL reference of what a belly filled with more than 4L of food looks like on a slender girl so i have to just wing it. There may be just as many people who think the volumes are too low as there are who feel like the volumes are too high, so I will need more opinions on this before I take action
breast growth depends on whether modding can fix a distortion issue with larger breasts on a huge belly. i do not know of any existing mod that fixes this. I can try to join a koikatsu modding server and ask for advice, but nothing is guaranteed. I do want this though
weight gain that significantly changes the shape of the body is not supported by koikatsu at all (and I am not personally into that), so the most that you can expect is a sort of baseline minimum of tummy volume that affects the tummy only. I would say to not get your hopes up if weight gain is what you want. (the project is not tagged weight-gain and is not advertised as such)
also, development of this game is on pause while I work on a different belly-related project for this month, check the devlog for more details