STRONGEST GUIDANCE (federal practice guide, WWC evidence levels printed)
🎮 Slime bars and the Goo Splat number line: 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).
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.
CORRELATIONAL (predicts, does not prove)
🎮 Why a whole game about fractions: 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.
Siegler et al. (2012), Psychological Science. National Mathematics Advisory Panel (2008), Final Report, US Department of Education.
DESCRIPTIVE (documents the errors we design against)
🎮 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.
Ni & Zhou (2005), Educational Psychologist: the whole number bias. Mack (1990), JRME: informal fraction knowledge and its limits.
HONESTY LINE: Numbercade is ESSA Tier 4 (research-based design). The studies above are about how fractions are learned in general. No study has tested THIS game, and we do not claim product-level efficacy. Lessons before challenges, worked examples, mixed review, and misconception-driven distractors are the design principles we borrowed; the slime explosions are ours.