Number Monster Instructions:

First, pick what you want to do: addition, subtraction, multiplication or division.
Then, pick your level...

For addition:
easy = single digits...  like 8+3
easy2 = a two-digit number plus a single-digit number...   like 63+8
medium = up to three-digit numbers...  like 73+345
hard = positive and negative numbers, up to two digits...  like -23+8
harder = positive and negative numbers, up to four digits...  like -2134+8764
killer = decimals

         For easier decimals, check out Coolmath's Decimals Cruncher
monster = positive and negative decimals

The Number Monster will keep track of your score.  When you move to a new operation (addition, subtraction, multiplication or division), your score will start over again.