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Red Blob Games

@redblobgames.com

1.5K followers 98 following 330 posts

Hi! I'm Amit Patel. I explain algorithms and math with interactive web pages (incl. pathfinding, hexagons, procgen maps, voronoi). Wrote Solar Realms Elite; helped w/Barren Realms Elite and Realm of the Mad God. https://www.redblobgames.com/

www.redblobgames.com

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Red Blob Games @redblobgames.com · 1d

I wrote this up in a blog post but I think the comparison screenshots show that the improvement is minor www.redblobgames.com/blog/2025-10...

Mapgen4’s use of WebGL2

www.redblobgames.com

Reposted by Red Blob Games

shri @shrikhalpada.dev · 1d

The question of "should I cooperate" shows up everywhere, from biology to geopolitics.

In my latest PerThirtySix piece, we explore the Prisoner’s Dilemma, starting from the basics and building up to population-level dynamics through interactive simulations!

perthirtysix.com/tool/prisone...

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Reposted by Red Blob Games

Pascal Mamassian @mamassian.bsky.social · 21d

A nice shift in perceived colour between central and peripheral vision. The fixated disc looks purple while the others look blue.

The effect presumably comes from the absence of S-cones in the fovea.

From Hinnerk Schulz-Hildebrandt:
arxiv.org/pdf/2509.115...

An array of 9 purple discs on a blue background. Figure from Hinnerk Schulz-Hildebrandt.

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Reposted by Red Blob Games

𝕮 @chrisshank.com · 9d

You can just make things on the web collaborative by adding a single HTML attribute...

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Red Blob Games @redblobgames.com · 3d

This is what I would expect. In calculus terms, "News" is the first derivative of the information, not the information itself. Unchanging information isn't "new".

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Red Blob Games @redblobgames.com · 4d

Yeah! I like <output> but don't use it fully, and haven't done enough for screen readers. I've mostly used this to display the result of <input> elements, like this:

Diagram from https://www.redblobgames.com/maps/noisy-edges/ showing the html structure for accessibility, including a <label> element surrounding an <input> and corresponding <output> element

Red Blob Games @redblobgames.com · 6d

Minor request: could you link to the corresponding caniuse pages for these features, so that a year from now if someone's reading your page they can see if there's any progress from Safari? e.g. caniuse.com?search=final... and caniuse.com?search=dispose

"finalizationregistry" | Can I use... Support tables for HTML5, CSS3, etc

caniuse.com

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Red Blob Games @redblobgames.com · 6d

Woah!!

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Reposted by Red Blob Games

Hillelogram @hillelwayne.com · 20d

I have a sparkling new blog post for you all! "A Very Early History of Algebraic Data Types" traces the history from the first innovation by John McCarthy, through its early use in imperative programming, and to its mainstreaming in FP. Come check it out!

www.hillelwayne.com/post/algdt-h...

A Very Early History of Algebraic Data Types

Been quiet around here! I’ve been putting almost all of my writing time into Logic for Programmers and my whole brain is book-shaped. Trust me, you do not want to read my 2000-word rant on Sphinx post...

www.hillelwayne.com

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Red Blob Games @redblobgames.com · 9d

Also notice the difference in the black line for the coastline — much smoother in the new code

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Red Blob Games @redblobgames.com · 10d

yay!

Red Blob Games @redblobgames.com · 10d

I could, but there were also weird artifacts that I didn't like, so I'm looking for ways to intentionally add noise (maybe blue noise) without getting the other artifacts. But it's more work than putting the bug back in ;)

Red Blob Games @redblobgames.com · 10d

Yeah, it's because I was storing the elevation in two bytes, and the low byte got scrambled, so some of the elevations end up being higher or lower than they should be. And those glitches are at regular intervals, so it kind of looks neat :)

But now I am storing elevation as one float

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Red Blob Games @redblobgames.com · 10d

I've been fixing numerical precision issues in #mapgen4 but some of those issues led to interesting textures that I liked.

(It may be hard to see them on the screenshots)

I'd like to have interesting textures that are intentional instead of the result of a bug …

mapgen4 render with a floating point precision bug

mapgen4 render with floating point bug fixed looks smoother

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Red Blob Games @redblobgames.com · 11d

btw this discussion reminded me of x.com/andy_matusch...

Andy Matuschak on X: "Alan Kay once said: "Turn up your nose at good ideas. You must only work on great ideas, not good ones." Inspiring, and exasperating. I've been grappling with it for years, on and off. Held as a lens, it really has pushed me to work on projects that have felt a lot more https://t.co/ELyTVkOtha" / X

Alan Kay once said

x.com

Red Blob Games @redblobgames.com · 11d

wow, nice!

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Red Blob Games @redblobgames.com · 11d

You can play with it now on www.redblobgames.com/x/2524-mapge... and I will push it to the main mapgen4 page after more testing

Mapgen4 Renderer

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Red Blob Games @redblobgames.com · 11d

I'm working on a slider that lets you control how deep the "folds" on the #mapgen4 mountains are

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Red Blob Games @redblobgames.com · 12d

New blog post: rewriting the mapgen4 river render www.redblobgames.com/blog/2025-09...

I had been drawing river segments on the cpu to a texture, and then reading that texture on the gpu. I changed it to draw river segments on the gpu directly.

Old river renderer: draw to the cpu, then read from that on the gpu

New river renderer: draw directly on the gpu in a shader

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Red Blob Games @redblobgames.com · 12d

oops!

Red Blob Games @redblobgames.com · 12d

oops!

Red Blob Games @redblobgames.com · 12d

I'm outputting to a WebGL R16F texture in mapgen4. It has a float channel, so I thought … I can set my frag shader to write to "out float" instead of "out vec4". But nope! :) I will change it back to "out vec4" and output three dummy values, which get thrown away.

(I'm learning WebGL2 this week)

Screenshot of buggy output from my shader

Reposted by Red Blob Games

Julia's Reruns Bot @b0rk-reruns.jvns.ca · 12d

how I got better at debugging

permalink: wizardzines.com/comics/bette...
from our free zine "So you want to be a wizard": wizardzines.com/zines/wizard/

A comic about computing. A transcript may be available at the link in the post.

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Reposted by Red Blob Games

Julia's Reruns Bot @b0rk-reruns.jvns.ca · 14d

tips for reading code

permalink: wizardzines.com/comics/tips-...
from our free zine "So you want to be a wizard": wizardzines.com/zines/wizard/

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Red Blob Games @redblobgames.com · 14d

New blog post: after a long break, I'm upgrading some of mapgen4's code (features, performance, bugs, ui, etc.) www.redblobgames.com/blog/2025-09...

A screenshot of mapgen4's map generator, with an ocean to the east, a land mass to the west, and a peninsula to the southeast