enter image description here

Users have to make the number on top (39) by using this numbers in the grid. In this case, they would tap 7 and 5 and swipe right to multiply. This converts the 7 in 35 and the 5 in a dead or used cell. Then they select all and swipe up to add them and make 39.

I want users to be able to undo moves, and they have a button alongside other buttons like go to the next or previous level to do so. But this is UX and I want the undo action to be a gesture too and I don't know which one is best: tapping a used cell once to undo or double tapping anywhere in the screen that is not interactive, like the background outside the board or, again, used cells.

  • Tapping once in the background is too broad.
  • Tapping once in a dead cell requires the user to "find" a dead cell. They are clearly visible but their position changes from level to level.
  • Double tapping in the background brings to the users a constant interaction across all levels they can quickly rely on. But double tapping is evil, right?
  • It is hard to imagine the exact problem and possibilities without an image. Can you add what is designed?
    – jazZRo
    Nov 26, 2021 at 9:21
  • @jazZRo Added image and description of playability
    – Bugzilla
    Nov 26, 2021 at 9:58

2 Answers 2


The best way to find out if gestures work is to test! Also provide a tutorial and have a help section always available to look them up. Be realistic on how familiar players will be with the game. To give some feedback on your ideas for undo gestures:

You are right that (double) tapping the background is a bit arbitrary.

Tapping a "dead" cell to undo raises a lot of questions: Which one to tap when there are multiple dead cells? Can you also tap dead cells from a few moves earlier? And will that undo the current move only or also that earlier move? It is maybe the better idea to undo but I don't think it is particular clear.

I would add a button for undo. But it concerns me that the design relies so much on icons! What I assume is the reset icon can also be an undo icon. Don't you think players will think that too? (again: Test!)

An idea to overcome the ambiguous icons is to use text instead. And add a help section to lookup how the game works.

enter image description here

  • For the icons vs text, the problem I see is that, for example in Spanish, undo and reset are much longer words and probably would clutter the screen. On the other hand, icon and numbers are universal. I'm still doubtful about the gesture system. I made a prototype with the tutorial and basic gameplay. I know it's asking too much, but you know your craft and your feedback would be much appreciated. It has no auth wall, ads or tracking,
    – Bugzilla
    Nov 29, 2021 at 10:47
  • You are right that labels can become problematic in small spaces. On the other hand can it be very frustrating that what you think is the undo button suddenly resets the whole puzzle! Is it needed to have a reset button in view, or is hiding it under a (popup) menu also possible? If so, you can use that icon for the undo button. I'm afraid it is hard to answer your question, it all comes down to testing multiple designs on potential users.
    – jazZRo
    Nov 29, 2021 at 11:49

There is an existing gesture for undo / redo actions which is the shaking the device, described at apple human interface guidelines.

If the option to shake the device is not a valid alternative, there's the possibility to implement the swipe left (if it has no other action assigned) or the 3-finger swipe as used in Android devices to delete emails from the mailbox.

Three-finger swipe: Initiates undo when swiping left, initiates redo when swiping right.

  • Swiping is not an option as swiping up, down, left or right is another fundamental part of the game, each direction having unique consecuences, sorry for not mentioning it. I think tapping in a empty cell or double tapping in non interactive elements is the way to go, but I can't decide between the two.
    – Bugzilla
    Nov 26, 2021 at 9:17

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