R3CK0N
R3CK0N is a free speed trainer for mental calculation. Every drill is timed and scored on speed, accuracy and consistency, and your history is kept so you can see the numbers move.
It has three training modes — Math for the four operations, Secret for the techniques in Secrets of Mental Math, and Zen, a numpad typing test — plus a Daily Challenge and head-to-head duels in the Arena.
No account is needed to play. Signing in syncs your runs across devices and puts you on the leaderboard.
JavaScript is needed to play.