There are tons of math games on the internet. Some are good, some are boring, and some make you wonder where the math is. Occasionally you find a game that really stands out as a great blend of math and real engaging fun. Gate is a game that was shared with me the Institute for Innovation in Education conference over the summer. It's awesome.
The story behind Gate is pretty epic, which adds a cool level of engagement to the game. It's art is really hip, and the gameplay is smooth, simple, and works well. You're destroying monsters from another dimension, but in order to use your magic staff, you need to build numbers correctly and quickly. It rewards players for knowing how to compose numbers using base 10 efficiently. As levels progress the ability to move up and down the number line becomes increasingly important.
Gate throws in some smart curveballs too, including blocks that float with a certain 'plus' or 'minus' to them. It intentionally exposes kids to patterns of our base 10 system and rewards them by using these patterns to be more efficient. I'd recommend the game for anyone 3rd grade and up who need practice with base 10. It's challenging enough to appeal to proficient mathematicians and offers great insight for all mathematicians.
Picture from: https://www.graphite.org/sites/default/files/experience-media-file/mathsnacksgate_ss1.jpg
Instructional Technology Coach