Learn
Practice vocabulary, visualize algorithms, explore concepts — learn by doing, right in your browser.
All Learn
Bopomofo Practice
Trace all 37 Bopomofo (Zhuyin) symbols (ㄅ ㄆ ㄇ…) in Taiwan's official MOE stroke order, with animation, live grading, and audio — for learners of Chinese.
Chengyu Guess
A daily four-character Chinese idiom guessing game with a multi-layer hint system. Six tries to crack the hidden idiom.
Chord Finder
Interactive chord diagrams for guitar, ukulele, and piano: look up any chord's fingering, or tap the fretboard to name what you're playing. With alternate voicings.
Contour → Terrain Profile
Drag a cutline across real terrain and watch the contour map and the cross-section move together. 14 real places from SRTM elevation, with vertical exaggeration and an adjustable contour interval.
Illusion Ruler
Nine classic illusions, measured on you. Adjust each figure until the two look equal and see how far off you were — every illusion also runs a no-context control trial, and the difference is the real number.
Moon Phase
See tonight's moon or any date: an astronomically-correct disc, illumination %, moon age and lunar day-of-month. Drag the lunation arc to sweep the terminator continuously. Includes a birth-moon share card.
Scale Sense
Translate any big number into real-world equivalents — 245 hand-picked anchors, from the speed of light to a bubble-tea cup, so abstract magnitudes feel real.
Stroke Order Practice
Trace common Chinese characters in Taiwan-standard stroke order — every character verified against CNS11643 official data, with live grading and stroke animations.
Sundial Simulator
An interactive sundial for understanding solar geometry — adjust latitude and date to watch shadows move.
Related categories
Frequently Asked Questions
What learning tools are available?
Ten. For Chinese: stroke-order practice and Zhuyin practice (both checked against Taiwan's Ministry of Education stroke data) and a daily four-character idiom puzzle. For English: spaced-repetition vocabulary on the Ebbinghaus curve. Most of the rest make something abstract visible — a chord finder for guitar, ukulele and piano, a moon phase viewer, a sundial simulator, a real contour map that draws its own terrain profile as you drag a cutline across it, and a tool that translates huge numbers into things your body understands. The last one runs the other way: the illusion ruler does not show you illusions, it measures how strongly each one works on you.
My child is learning to write — where do we start?
Kindergarten to first grade: start with Zhuyin practice — all 37 symbols, each with a stroke-order animation and live checking as the child traces. Once the symbols are familiar, move to stroke-order practice, which covers common characters with the Ministry of Education's official stroke order and marks a wrong stroke the moment it happens. Neither needs an account, and nothing is sent anywhere.
Does progress save between sessions?
Yes, in your browser's local storage, so you can pick up where you left off. It stays on that device — there is no account and no sync, which also means clearing site data clears the progress.