The game is fun for a while, not complicated but good mindless fun. Unfortunately the math is pretty rough, particularly around negative numbers. If you try to stack up the negative values then subtract them it just sets your number to zero rather correctly calculating the value. Similarly, if you multiply by a negative number, it does allow you to get a negative value, however if you try to add or subtract anything from that, it’ll (again) just set you to zero. Luckily, multiplying two negative numbers does function properly and is often a good strategy.