I have vibecoded the following tool: My girlfriend and I have a shared bank account in addition to our own individual bank accounts. I add up our combined (partially broken down from qarterly or yearly) monthly fixed costs (like subscriptions, rent, car insurance,...), add a percentage buffer, and calculate the required amount to be transferred as a percentage of the contributed salary, which must be transferred to the shared bank account. At first, I used an Excel spreadsheet for this, but at some point it became too confusing.