Given a task such as 'construct the centre of a circle', players use only a straightedge and compass (plus tools they unlock) to build it, earning stars for using the fewest lines and elementary moves; later packs demand genuinely clever constructions.
Why it may be useful
Constructing a figure with only a straightedge and compass is classical geometry itself, not a theme around it, and the move-count scoring pushes you from any solution toward an elegant, proof-like one.
Keep in mind
Progress is gated behind earning stars or paying for the mobile unlock, difficulty rises fast, and it teaches construction reasoning rather than the coordinate geometry most school exams test.
Written 2026-09-15 · editorial assessment, not a measured effect · how we rate →
What the game is
Euclidea is a geometry puzzle game by HORIS International, a small Hong Kong developer, first released in 2015. Each level states a construction task, build the center of this circle, bisect this angle, inscribe a square in this triangle, and gives you a blank canvas with a straightedge and a compass. Those are the two tools Euclid allowed, and no others are permitted.
The screen is a white sheet with the given figure drawn on it. You drag to place a line through two points or to swing a circle from a center through a point, and the intersections you create become new points to build from. A construction is checked exactly rather than by eye: the level opens only when the required object genuinely exists.
Levels are grouped into packs that unlock as you go, and the official site lists more than a hundred and twenty of them. Four shortcut tools, the perpendicular bisector, perpendicular line, angle bisector and parallel line, are earned rather than given, by first building each one from scratch.
What you actually do
You are scored twice. The L count is the number of tool moves you used, and the E count is the number of elementary straightedge-and-compass steps underneath them. Stars are awarded for reaching a par on each, so a solution that merely works is only the start, and the game then quietly asks whether you can do it in fewer moves. That is the loop: solve it somehow, look at the par you missed, and go back for a cleverer construction. Difficulty climbs steeply. Early levels take a minute; later ones ask for genuinely hard constructions, and progress is gated, because stars from earlier packs are what open the later ones.
What it exercises
Builds a required figure from two primitive tools and nothing else
Reasons about why a construction is correct, not just that it looks right
Searches for a shorter method after already having a working one
Recognizes a standard construction hidden inside a larger problem
Uses a result established earlier as a single step later
Why we rate it Exceptional Worksheet score 86 / 100
FitHow much real knowledge or skill does the play itself make you use?92weight 45%
Fit is 92, near the very top of the scale. The mathematics is not a theme wrapped around a game; the construction is the game. There is no scoring layer on top, no story and no dexterity involved, and the only way to pass a level is to perform a valid Euclidean construction. Very little else comes this close to the real discipline.
TransferWill what you practise here work outside the game?82weight 30%
Transfer is 82. Constructing a figure and then justifying why it works is close to the reasoning school geometry actually asks for, and the move-count pressure pushes a student from any answer toward an elegant one, which is what a proof rewards. It falls short of the very top only because most exams test coordinate geometry and algebra rather than compass work, so the overlap is real but partial.
PracticeDoes the game make you use that skill again and again, as it gets harder?80weight 25%
Practice is 80. The same construction reasoning repeats across more than a hundred and twenty levels, and chasing the par move count means replaying levels already solved to find a shorter path. It stays out of the very top band because the star gate stops many players before the end, and the content, unlike an endless puzzle generator, eventually runs out.
What the evidence says
Editorial onlyNobody outside our desk has checked this. It is our reading of how the game plays.
The evidence level is Editorial only. The sources are the official site and the App Store and Steam listings, checked in September 2026, with the official site re-read here. Together they confirm the developer, the 2015 origin, the straightedge-and-compass rule set, more than a hundred and twenty levels, the four shortcut tools that must be earned by construction first, the fewest-moves scoring, and the free-to-start mobile and browser routes. None of them is a study, and none exists for this game. The strong editorial reading rests on one fact: the puzzle performs classical geometry exactly, checked by a system that rejects any construction that merely looks right, rather than approximating the subject loosely.
Editorial assessment - not a measured scientific effect.
Fit
92/100
Transfer
82/100
Practice
80/100
Why it makes the cut
A scored puzzle progression with star ratings, unlocks and a devoted community chasing minimal solutions; the maths is the puzzle rather than a wrapper around it.
Editorial only
Editorial only, based on the official site and the App Store and Steam listings; no study of Euclidea or of construction-based geometry games was found.
Play on web ↗HORIS International · Checked 2026-09-09
Prices are US store listings in USD, last refreshed 2026-09-28; regional prices and sales differ.
Pythagorea, by the same studio, offers easier grid-based geometry puzzles for slightly younger players.
Age guidance
Ages 12+
Topics
STEM, Logic & strategy
Play styles
Single-player, Puzzle
Tags
Geometry · Constructions · No ads
It sits at the top because the construction is the whole game, with no scoring layer, no story and no dexterity test on top of it, and the move-count pressure pushes toward genuinely elegant solutions.
