Note: Many of these examples are written in terms of circumstances of X and how O can be affected by them; X and O can, of course, be reversed.

• Whenever you get stuck, remember to check the three rules:

  • Are there any places where a pair of Xs next to each other, which you can surround with the Os? Don't forget to look for pairs of Xs separated by one space; you can put an O between them to prevent a three-in-a-row.

  • Are there any rows half-filled with one symbol? Use the left and top edges to quickly check the current symbol totals; the numbers in the corner (in black) are the target numbers to reach. If one symbol matches that number, fill in the rest of that row with the opposite symbol.

  • Are there any potential duplicate rows that can be avoided? Look for nearly-finished rows (usually with two spaces open) and compare them to rows that have been finished.

• If you have a row that's missing only one X but a couple or more Os, try putting the X in each of the remaining spaces, and see if that forces a three-in-a-row of Os. You can usually fill in many Os with this method, if not the whole row. For example, in the screenshot above, if the last X was placed in the second or third spot in the third column, it would force three Os in a row below. Thus, both of these squares must be Os to prevent that.

• Don't forget your good pals Trial and Error! You can use the pencil tool in the top bar to make small Xs and Os to test out possible answers before you mark them in fully.

Easy Starters

Medium Starters

Hard Starters