Timed mental-arithmetic trainer. Choose an operation and difficulty, and race the clock — tracks streaks and personal bests in your browser.
▶ playTools, games and curiosities — made for fun.
Smaller side-projects that don't fit neatly into research. Free to use.
Timed mental-arithmetic trainer. Choose an operation and difficulty, and race the clock — tracks streaks and personal bests in your browser.
▶ play