thanks for playing!!! let me try and explain:
i was originally planning an ending requiring you to fund a weapon that could finally put it down for good, meaning you would have to balance funding it with keeping the kaiju at bay, buuuut i ran out of time, so i quickly just whipped up a day counter instead and said "see long you can last" lol
the code just takes whatever stats you had when you beat it and adds half of it to it's defence (but not higher then your current attack). After a point you WILL do 0 damage and lose no matter what, but so long as you make any upgrade you should be able to kill it in time.
I might make a revised version or a sequel to fix things i wasn't able to get done on time, it was a fun project :)