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@mrflip
Last active January 12, 2026 08:07
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Ancient Greek Geometry walkthrough / answers / cheats

Solutions for Ancient Greek Geometry (https://sciencevsmagic.net/geo)

Most solutions taken from the about thread. See the comments below for more additions since my last check-in.

Polygons

Circle Packs

Circumscribed Polygons

Non-Constructible Figures

Abuse of floating-point math can make the widget approve non-constructible polygons (polygons with edge count 7, 9, 11, 13, 14, 18, 19, 21, 22, 23, 25, 26, 27, 28, 29, 31, 33, 35, ..., which cannot be precisely constructed using straightedge and compass):

@Eddy119
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Eddy119 commented Sep 27, 2025

Ok, I just got the nonagon (9-gon) down from 34 to 31 moves OLD NEW² UPDATE: nonagon aka 9-gon in 27 moves

Since I'm posting, gonna post the other things I've been up to:

  1. As for my symbolic logger attempt, I can't find a algebra library that can rationalize the denominator, so the logger freezes when it outputs and works with $\frac{7985/4 + (3571/4)\sqrt{5}}{(2+\sqrt{5})^6}$ instead of $\frac{5-\sqrt{5}}{4}$ for $\cos\left(\frac{3\pi}{5}\right)+1$, for point 14 here on a pentagon with top point at (0,0) centered in a unit circle centered at the right origin point (1,0).
    If any of you guys have a clue on how to fix this, please help me... I gave up for now. I wrote up about this issue here.
  2. The 11-gon is neusis constructible (this game doesn't have neusis) according to this paper, but I found only one claimed construction method, which is on Reddit, and it involves fitting a circle, which is a bit more than neusis, which you fit a line of a specific length between two lines or circles or a circle and a line. If you guys can find a way to do an exact neusis construction, please tell me here...
  3. I tried emailing Nico (twice) if I can fork his game etc, but he still hasn't replied. Should I worry about copyright, if I want to modify and add more features, to the game, maybe make a v2...
  4. There's a similar (copyrighted) game to this called Euclidea.
  5. Edit: I/we should figure out the star trick for Doomslug682's polygons... later...

@Eddy119
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Eddy119 commented Oct 2, 2025

Here's a 17-gon done with Carlyle circles in 58 moves
Update: 57 moves
Update 2: 55 moves
Update 3: I figured the star trick out, now it's 49 moves, same as the Richmond method; Update 4: identical but prettier version

Sources: https://commons.wikimedia.org/wiki/File:01-Heptadecagon-Carlyle_circles.svg https://commons.wikimedia.org/wiki/File:Regular_Heptadecagon_Using_Carlyle_Circle.gif

Not sure if this method can potentially beat our existing 45/49 in-origin record, I'll paste this in case someone wants to try doing the star trick or other move optimizations, I'll try later

Update: I think it's theoretically possible to use Carlyle circles to get the 5th vertex (cos(10pi/17)) of the 17-gon, and this method might take less than 49 moves to complete; I'll have to learn how to draw Carlyle circles though.

Update 5: https://web.archive.org/web/20151221113614id_/http://apollonius.math.nthu.edu.tw/d1/ne01/jyt/linkjstor/regular/1.pdf the paper that contains this method also mentions the method can be simplified so if we do that and directly find the 5th vertex (or really any vertex on the "left" side), we might be able to save a lot of moves

Also, regarding the neusis of 11-gon paper (not this game): if we found out a way to solve cubics like we can solve quadratics with Carlyle circles, it's a matter of constructing u, then solving/constructing/doing neusis for "the rest" (easier said than done).

@Eddy119
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Eddy119 commented Oct 2, 2025

Right, I followed the simplifications in this paper and managed to reduce the move count for the 17-gon in origin to 44 moves.
https://sciencevsmagic.net/geo/#1A0.0A1.0L1.3L2.1A6.6A0.11L10.14A0.0L12.12L25.25L1.1L28.1L9.9L4.10L24.24A12.0L41.N.41A25.42A25.4A55.55A4.97L98.104A1.1A126.1L146.146A1.N.170L169.4L72.72L146.198A25.N.225A1.1A225.271L270.290L4.4L291.291A4.357L291.291L384.4L384.1A384.290L436.357L439.291L438.438L357.357L468.439L450.450L493.468L480.480L521.493L506.4L437.437L290.290L571.506L547.521L534.534L598.547L587.587L420.598L614.614L655.420L638.638L687.655L673.673L716.687L705.705L749.716L734.734L786.749L769.769L571.436L786

I suspect if we solve for the 5th vertex instead and do a version which is not in origin we can reduce the move count even further.

Update: Gonna try to solve for vertices 10,11,7,6 3,5,14,12 since they're next to each other so it's easiest to star...

Update 2: Another 44 move in-origin 17-gon using 3rd and 5th vertices UPDATE 3: 43 moves:
https://sciencevsmagic.net/geo/#1A0.0A1.0L1.3L2.1A6.6A0.11L10.14A0.0L12.12L25.25L1.1L28.1L9.9L4.10L24.24A12.0L41.N.41A25.42A25.6A71.1A78.96A1.112L113.55L96.144A25.N.174A1.1A174.220L219.220L238.219L239.1A0.239A4.238A254.254L288.254L314.1A314.288L348.348L4.4L364.356A4.356L365.365L238.356L393.365L412.238L411.365L394.393L288.288L436.412L424.424L459.459L394.436L364.314L493.493L520.520L4.4L545.545L254.254L568.568L513.513L597.597L535.535L625.625L560.560L653.653L238.238L682.682L614.614L710.643L471

Trying to figure out 6th and 7th vertices right now... Update 3: Seems like using the 3rd vertex is the simplest

@Eddy119
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Eddy119 commented Oct 3, 2025

If you double the circle that the 17-gon will be inscribed in instead of quartering the origin circle in the beginning, you can get 39 moves.

Not sure about other simplifications that can be done if 17-gon not drawn in origin circle, please share any progress.

@Eddy119
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Eddy119 commented Oct 3, 2025

Star trick optimizations:
9-gon, in-origin, approx, in 27 moves
11-gon, in-origin, approx, in 38 moves
Others here, please feel free to simplify the other ones through the star trick or other methods.

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

More heptagon relationships Tetradecagon in 24 moves: https://sciencevsmagic.net/geo/#0A1.1A0.0L1.1L5.5A2.6A1.9A2.0A17.19L18.26A1.N.1A43.43L19.59L0.43L18.18L86.0L81.0L96.96L19.19L102.46L102.102L118.118L5.5L130.130L86.47L140.140L153.153L5.102L110.110L127.115L175.150L18.139L162 Icosahenagon (what I call the henskaicosagon) in 30 moves: https://sciencevsmagic.net/geo/#0A1.1A0.0L1.1L5.5A2.6A1.9A2.0A17.19A2.N.2L27.27L34.1A34.34L3.3L57.2L49.34L35.35L3.3L66.34L50.50L2.2L76.76L5.5L83.66L5.5L90.65L27.27L106.75L51.51L118.49L80.80L129.57L87.87L139.118L136.106L126.90L67.67L183.139L178.83L59.59L216.129L213.216L98.183L113.272L249.229L149.196L161 Icosioctagon in 36 moves: https://sciencevsmagic.net/geo/#0A1.1A0.0L1.1L5.5A2.6A1.9A2.0A17.0L24.N.24L19.1A24.19L40.24L18.18L48.48L5.5L53.40L5.5L58.58L43.43L69.53L28.28L81.81L18.18L95.69L19.19L110.110L55.55L120.95L50.50L129.129L74.74L146.120L64.64L160.146L89.89L179.160L102.102L199.179L127.127L216.199L118.118L232.216L141.141L251.232L157.157L269.251L174.174L294.269L192.192L320.289L0.313L0.320L229.294L213.213L423.229L399.399L266.423L248.396L470.420L446 Tetracontakaidigon or Lifegon (since 42 is the answer to everything) in 50 moves: https://sciencevsmagic.net/geo/#0A1.1A0.0L1.1L5.5A2.6A1.9A2.0A17.N.2L19.19L27.3L18.18L33.1A26.33L2.2L56.2L45.27L3.3L64.3L46.56L5.5L71.64L5.5L78.46L75.75L87.45L68.68L95.71L57.57L110.95L105.105L126.78L48.48L143.87L136.136L161.55L18.18L180.63L19.19L199.110L193.193L220.143L175.175L239.161L235.235L262.126L215.215L285.199L92.92L306.180L84.84L326.239L323.262L346.220L303.285L393.326L154.154L449.306L121.121L477.449L257.257L509.509L370.477L279.279L572.572L417.303L396.396L474.474L635.393L420.420L632.632L669.417L602.602L666.666L704.635L567.567L746.0L739.704L0.505L813.701L536.323L349.349L446.346L373.373L929.370L539.539L966.599L1003

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

@mrflip can you change the 17-gon at the top from the 45-move to the current 38-move?* It's still the same.

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

When you use the 34-move nonagon, you can replace with the bisector of point 1 above main origin point and point 1 above the previous, then star instead to get 26 moves.

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

Using the star trick (on heptagon for example) on the icosanonagon and taking a different tangent, you can get 60 moves.

@Ian-Zander
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I've been trying to find the 31-gon through brute force, but floating point keeps getting in the way.

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

Yeah. Makes sense. Did you think it was even possible to optimize the heptagon?

@ILoveMath62
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ILoveMath62 commented Nov 18, 2025

I literally joined yesterday.

@Ian-Zander
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In your 37-gon attempt, move 26 scrambled (weird floating point stuff I don't understand). It basically places multiple lines at once

@Ian-Zander
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Something I've found while brute forcing is that changing the scale sometimes fixes it

@ILoveMath62
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ILoveMath62 commented Nov 19, 2025

I don't know where @pizzystrizzy, @bikerusl, @ralpjs, @mrflip, @Doomslug682, or @WaiLFiN went.

@Eddy119
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Eddy119 commented Nov 20, 2025

Hi, interesting stuff, I am here, I can't look at all of this right now, but I'll look into it I'm the near future, I'm still interested, and wondering how to neusis construct a 11-gon...

Maybe we should make a discord for all of this? It might make discussions easier...

(My discord is the same as my GitHub)

@Ian-Zander
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A discord sounds cool

@ILoveMath62
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Hint for faster possible 21-gon

@Ian-Zander
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Ian-Zander commented Nov 22, 2025

My game isn't accepting it
edit: I was tweaking

@ILoveMath62
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ILoveMath62 commented Nov 22, 2025

Approximations to be done for more shapes:
43 (approximation used by taking the tangent, please share) Late Nov update: I finished it!
44 (11x4)
45 (5x9)
46 (23x2)
47 (use by tangent, please share) Early Dec update: finished by me!
48 (2⁴x3)
49 (use by tangent, please share) Early Dec update: Finished by me!
50 (25x2)
51 (use triangle on heptadecagon, please share)
52 (13x4)
53 (use tangent, please share) Mid-Dec update: finished by me!
54 (3³x2)
55 (5x11)
56 (7x8)
57 (3x19) Mid-Dec update: finished by me!
58 (29x2)
59 (use tan, please share) New Year's update: finished by me!
60 (3x4x5)
61 (use tan, please share)
62 (2x31)
63 (7x9)
64 (2⁶)
65 (13x5)
66 (2x3x11)
67 (use tan, please share)
68 (4x17)
69 (might be done with trisecting 23-gon, but might fail, please share)
70 (2x5x7)
71 (use tan, please share)
72 (8x9)
73 (pierpont, approx.)
74 (2x37 [please share 37]) Late November update: 37-gon is finished!
75 (3x25)
76 (4x19)
77 (7x11)
78 (2x3x13)
79 (use tan, please share)
80 (2⁴x5)
81 (3⁴ [use tan, please share])
82 (2*41 [please share 41]) Thanksgiving update: 41-gon finished!
83 (use tan, please share)
84 (3x4x7)
85 (5x17 [perfectly constructible as being a multiple of two distinct Fermat primes])
86 (2x43 [please share 43]) Late Nov update: I finished the 43-gon!
87 (3x29)
88 (8x11)
89 (use tan, please share)
90 (2x5x9)
91 (7x13)
92 (4x23)
93 (3x31)
94 (2x47 [please share 47])
95 (5x19)
96 (2⁵x3)
97 (pierpont, approx.)
98 (2x7² [please share 49])
99 (9x11)
100 (4x25)

Italic involves trisecting an angle and Bold can only be made by taking the tangent.

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