There should be a confirmation for buying and selling anything, not just blue and red things. Also, the sell confirmation screen should say what you're selling and give a warning if you've used it a lot, and maybe if you've had it for a while.
There should be something to confirm going down stairs. I missed an artifact on floor 38 because I accidentally went one square too many when I was trying to get to it and went down the stairs.
 "Astrox"){kind=icon}
 "Another Pointless Flash Button Game Derived From Other Pointless Flash Button Games Inspired For No Absolute Reason Featuring a Random Button That Asks You Random Pointless Objects and Challenges You (Yes you.) To Complete This Super Long Game If You Can"){kind=icon}
 "Obliterate Everything 3"){kind=icon}
 "The Enchanted Cave"){kind=icon}