FRACTIONS · RATIOS · PERCENTS
HOW TO PLAY Raise a pet slime at every lab station. Feed it exact portions: every correct answer makes it grow. Fill its meter and it EXPLODES into bubbles, stars, or goo. Lessons teach first. Hearts refill with a quick review.
🎁 You earned coins! Spend them in the Avatar Lab on the main menu.
No stars, no hearts, no pressure. Each station serves 15 at a time. Earn a gem for every one you crack (up to 15 a day). Miss one and ANOTHER LIKE THIS serves a twin.
Rework the ones that got away. Each correct answer patches one heart.
A slime slides along the number line. SPLAT it exactly on the target fraction. Five shots. Bullseyes earn gems.
Slime Lab teaches a skill first, then has kids practice it, with no clock and no way to fail out. Every fraction is drawn as a slime bar on a measurement model, and every wrong option is a documented misconception. Each design choice below implements a practice with independent research support. The studies test the practice, not this game; we make no product-level efficacy claim.
Every fraction in this game lives on a measurement model, not just a pizza. The What Works Clearinghouse practice guide on fractions instruction recommends making number lines central to teaching fractions; the panel rated that recommendation MODERATE evidence. Its recommendation to build early fraction ideas from fair-sharing activity is rated MINIMAL evidence, and the guide also urges teaching WHY computational procedures work, which is how the Goo Press teaches mixed-number addition. A newer WWC practice guide on elementary math intervention rates its own number-line recommendation STRONG evidence (for students struggling with math, the guide's population).
GUIDE Siegler, R. et al. (2010). Developing Effective Fractions Instruction for Kindergarten Through 8th Grade (WWC practice guide, NCEE 2010-4039). Fuchs, L. S. et al. (2021). Assisting Students Struggling with Mathematics: Intervention in the Elementary Grades (WWC 2021006), Rec 4. Evidence levels as printed in the guides.
A longitudinal study of US and UK students found that fraction knowledge at age 10 predicted algebra knowledge and overall math achievement at age 16, over and above IQ, family income, and whole-number skill. Separately, a national panel survey of 743 Algebra I teachers rated poor preparation in "rational numbers and operations involving fractions and decimals" among the biggest gaps in their students' readiness.
CORRELATIONAL Siegler et al. (2012), Psychological Science. National Mathematics Advisory Panel (2008), Final Report, US Department of Education.
The add-tops-and-bottoms trap in the Goo Press (1/4 + 2/3 is NOT 3/7) and the bigger-denominator-means-bigger trap in Splash Tank are there on purpose: research on "whole number bias" documents how children carry whole-number rules into fractions and make exactly these errors. Distractors in this game are those documented misconceptions, so a wrong answer teaches something specific.
DESCRIPTIVE Ni & Zhou (2005), Educational Psychologist: the whole number bias. Mack (1990), JRME: informal fraction knowledge and its limits.
No study has tested this game itself. Lessons before challenges, worked examples, mixed review, and misconception-driven distractors are the design principles borrowed from the research above; the slime explosions are ours. See numbercade.com/why-it-works.