STEM
FractionForge
Master fractions, decimals, and place value through virtual manipulatives, number line challenges, and real-world problem contexts — following the research-backed Concrete-Representational-Abstract instructional model. Grades 4–6 (about ages 9–12).
▶ Play it nowBuilt for sittings of about 20 minutes on the screen. That is our design budget, not a measurement.
👥 Pass-and-play available
Meet your mentor
Every Spark & Anvil app has a friendly mentor character that demonstrates, asks, and patiently scaffolds learning. On-device AI personalizes the mentor's responses to your kid's progress — never connecting to a server, never collecting data.
Mentored by Halver
#29B6F6 FractionForge makes fractions and decimals easy to understand! Start by playing with virtual pizza slices and fraction bars you can touch and move. Then see how those pieces turn into diagrams. Finally, work with the numbers and symbols. This step-by-step approach (called Concrete-Representational-Abstract) is how the best math teachers in the world teach fractions!
Characters who teach
Meet the cast
Each character in FractionForge is one fraction idea: cutting a whole into equal parts, wholes and mixed numbers, equivalent fractions, common denominators, decimals and percents, the number line, adding, multiplying, place value after the point, and comparing.
Halver
Partitioning — splitting a whole into equal parts (denominator construction)
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Pie
Wholes and parts — mixed numbers, improper fractions, whole-as-pie anchor
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Equi
Equivalent fractions — different forms, same value (×n/×n scaling)
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Stretch
Common denominators — scaling to a common base for comparison + addition
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Dot
The decimal point and fraction-decimal-percent equivalence
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Liner
Number-line placement — every fraction has an exact spot between the whole numbers
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Gather
Adding and subtracting fractions — you can only combine pieces that are the same size
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Times
Multiplying fractions — a fraction OF a fraction, shown as the overlap of two strips
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Tenth
Decimal place value — each column right of the point is ten times smaller
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Rank
Comparing and ordering fractions using benchmarks and reasoning
Read chapter →
Browse all chapters → · What's distributed-narrative methodology? →
What's inside
Manipulative Workshop
Touch, drag, and split fraction pieces. Break a pizza into thirds, compare half to three-sixths, or stack fraction bars to see which is bigger. This is hands-on
Number Line Arena
Place fractions on a number line and see where they belong. Is 3/4 bigger than 2/3? Put them on the line and find out! Race to place fractions accurately for bo
Operation Lab
Add, subtract, multiply, and divide fractions using visual tools. See what happens when you add 1/2 and 1/3. Watch the pieces combine on screen.
Decimal Bridge
Connect fractions to decimals. See that 1/2 is the same as 0.5, and 1/4 is the same as 0.25. Build bridges between the two systems.
Mentored by Halver — on-device AI, no data leaves the device.
How FractionForge handles your kid's data
- ✅ All progress, settings, and AI-generated content stays on the device
- ✅ No analytics, no tracking, no third-party SDKs
- ✅ Free — no ads, no in-app purchases
- ✅ No personal information collected from children — in line with COPPA (updated by the 2026 FTC amendments)
- ✅ No chat with strangers — play-together rooms use a short code and preset emotes, never typed messages
For you, the grown-up
The grown-up side of FractionForge on Spark & Whetstone, our free site for grown-ups: Fractions for Grown-ups. Bars, pies and number lines, the way fractions are taught now.
It also tells what FractionForge teaches in a short course of its own.
FractionForge runs on ForgeKit — the open-source Swift Package Manager framework that powers every Spark & Anvil app. ForgeKit ensures consistent accessibility, COPPA compliance, and design language across the portfolio, so your kid's progress and preferences feel coherent across every app they touch.
Coming to the App Store
FractionForge is in active development. Email us to hear when it ships — no marketing, no spam, just a one-shot launch announcement.
Email me at launch
