UX quiz:
a) trim whitespace characters from credit card or bank account input
b) refuse transaction, show error message: "no spaces are allowed in the card number"

as a bonus, make it inconsistent across your company's services, i.e. Bing vs. Microsoft account, and don't offer to sync both, you must make the user enter all data redundantly.

Bing offers to "sync" data from Google (not vice versa) but if you have any existing data in your Microsoft account, there's no way to fetch that.

Bing won't accept a credit card that Microsoft validated successfully just minutes before. That's top UX! We must learn from Microsoft's experience!

Also make sure to request that the user has to log in again for each new sub-service of your company. When they do, block their login attempt and show a message:

Something went wrong and we can't sign you in right now. Please try again later. The Microsoft account login server has detected too many repeated authentication attempts. Please wait a moment and try again.

Do everyhing you can to prevent users actually using your service, even if they are willing to pay for it. Make everything extra hard so that only the most creative and stubborn people will eventually make it after days or weeks. But if they succeed, that may prove they are not humans but robots after all.

When they still don't give up, accuse them of violating your policies, but don't give any hint what exactly they might have done.

bonus points: limit the input to _exactly_ the length of a credit card number (or whateve), so when copy-pasting one _with_ whitespaces, part of it is cut off.

refuse transaction, clear the entire form, reject any submission in the next minute for ddos protection while also resetting the ddos protection timeout on that rejected submission.

cache all credit cards that ever declined and reject them. Also cache which credit cards were used by which user and reject cards for all other users until the first user asks customer support to remove the card. There should be no automated way to do this.

Prevent copy and paste, add groups of inputs without clear indicator of how many digits they accept nor if they should have space. Upon typing space, jump to next group and make it quite hard to bring the cursor back to the correct position when space was pressed.

Make it so the X-digit long number is actually X separate fields, not allowing for tab and certainly none of that automatically going to the next field crap. Also, make a repeat for verification with asterisks after entry and a timer for their privacy protection

finally, surprise returning users with a dubious rewards programme and when they click on it then throw another error with a cryptic hash id and a supposedly friendly/funny line like "it’s not you, it’s us" plus the inevitable "something unexpected went wrong...

Ooo there needs to be one of those 90s (still occasionally now) redirect pages where it says youll be redirected in ~10sec, if not, click this link... but the link is state refreshed beginning.

@idkhow
When jumped to next field before proper input, mark previous fields value as faulty. When skipping back, mark next field faulty - cause empty?? Duh!
Love the space skip to next field.

Nobody mentioned marquee yet or sounds. Defs missing a tap tone for every digit at least!

@dder nah if there's gonna be sounds when u enter a digit it should be that slighty dated sound from windows when there was a, often unseen, error or u were trying to click something that wasnt at the top of the priority stack... that sound im pretty sure caused more ptsd and startled awake nightmares than war. I think it may actually be the sound of anxiety