it seems I have to hit enter twice every time (windows 10, chrome,firefox & edge). also when you enter too big a number you get "seed must be an integer". I think you should accept anything (build your seed digit by digit and let it wrap around its 32bits). even better yet, make a hash from actual text, so you can actually name the planet!
not sure you need another button if you can debug the text box. the dice button should also generate the planet though.
nice little toy btw :)