Base 10 Blocks on your iPad!

I discovered the iPad app "Number Pieces" this past week.  It is a great way to have students work with base 10 blocks and it is FREE!

There are a couple of features that make this app really useful for students:
1.  Students can decompose or recompose numbers using the same blocks.  For example, if you want to break apart 1 ten into 10 ones, you click on the piece you want to separate and then touch the separate icon.  Alternatively, if you want to put 10 ones together to make 1 ten, lasso the blocks (a blue dotted line will appear) and then touch the "join" icon.  You could also lasso a large number of pieces to rearrange them into larger groups (such as moving 32 ones into 3 tens and 2 ones).
2.  If you want to subtract, you can change the color of the blocks.  This allows students to maintain the original amount without having to remove pieces, allowing them to see the part-part-whole relationship.  With the app, students don't have the confusion of trading the pieces and keeping track of their counting.  The app also includes a marker feature so students could draw a part-part-whole organizer or represent the computation.  See the picture for an example.

I'm sure you have many additional ways this app could be used with students.  I would love to hear your ideas!