connect three

this game from NRich provides good practice in adding and subtracting directed numbers - to get three in a line
play against the computer or a partner

eManipulatives: directed number

This site shows positive and negative counters (use the rubber stamp to include counters and the hand to move them).

It can be useful to show, for example, that taking away a negative counter results in a positive counter being added to the top pile.

To make the picture larger use Ctrl and your mouse wheel