STEM
NumberSense
Daily-prompt estimation app for ages 9-12. A 10-second estimate phase before every compute phase. Per-kid calibration card surfaces estimation bias over time. Wordle-template daily cadence.
Meet your mentor
Every Spark & Anvil app has a friendly mentor character that demonstrates, praises, 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 Estimator Ernie
#0EA5A5 NumberSense gives you one number question a day — and asks you to estimate first. Ten seconds. No pencil. No calculator. Just your gut. Then you compute. Then you compare. Over time you see your own bias on a calibration card and watch it shrink.
Distributed-narrative cast
Meet the cast
NumberSense's cast carries the estimation posture: confidently approximate first, calculate second. An estimate-first advocate, a question-flipper, a per-something specialist, and a make-10 / place-value specialist.
Estimator Ernie
Confidently approximate; the first-guess advocate
Read chapter →
Pivot Pia
Deceptively casual question-flipper; reframes the prompt
Read chapter →
Ratio Rio
Per-something specialist; rate thinker
Read chapter →
Splitter Sasha
Make-10 and place-value specialist; benchmark builder
Read chapter →
Browse all 4 chapters → · What's distributed-narrative methodology? →
What's inside
10-Second Estimate
Before every problem, you get ten seconds to gut-check. No calculator, no pencil — just your number sense.
Calibration Card
See your estimation bias over time. Are you a high-guesser? Low-guesser? Right on?
Daily Cadence
One question a day. Wordle-style. Streaks reward steady practice, not cramming.
Estimation Strategies
Front-end, rounding, compatible numbers, benchmarks — the cast embodies them one at a time.
Mentored by Estimator Ernie — on-device AI, no data leaves the device.
How NumberSense handles your kid's data
- ✅ All progress, settings, and AI-generated content stays on the device
- ✅ No analytics, no tracking, no third-party SDKs
- ✅ No ads, no in-app purchases — you pay once
- ✅ COPPA compliant under the 2026 FTC amendments
- ✅ Parental controls + session limits + content filters built in
NumberSense 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
NumberSense 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