Hello! Im Matheus Mendes and im a software engineer

Things I've worked on

Midjourney

Making images look good

Work

jefftube

A Youtube clone showing all of the released Epstein videos by the DOJ

TypeScript
49
94

Sideproject

Dema

Analytics platform for E-commerce

Work

codex

Lightweight coding agent that runs in your terminal

Rust
8
4134

Sideproject

css-only-rubiks-cube

A spinning Rubik's Cube with functionality all made with CSS only

CSS
13
21

Sideproject

daij

Listen and rank AI Generated music by Claude, ChatGPT and Gemini

TypeScript
2
70

Sideproject

vercel-ui

Design library inspired by Vercels design system

TypeScript
42
13

Sideproject

lucio

TLDR; Leetcode and CSS Battles into one platform

TypeScript
17
341

Sideproject

Acasting.se

Modern casting platform

Work

About me

I am a full-stack developer from Sweden with experience in web applications and apps.

Currently I work as a software engineer at @Midjourney, and also a scout for @a16z

hover action arrow
headshot

First line of code

First software engineering job

Total prod crashes

1 oops :(

Rank #1000 on CSS Battles

I really like CSS (I don't really get the hate), and one of my favorite sites is CSS Battles where you can compete with CSS. I used to play it a lot and at one point I got to rank 800, but now im sitting at around 1000. There is about 350k total users on the platform.

headshot

Matheus Mendes

53700.24 points
(84 Targets)
#1146
Tetris css battles

Rank #36 in the world

Tetris css battles

Rank #74 in the world

Tetris css battles

Rank #36 in the world

Tetris css battles

Rank #38 in the world

Tetris css battles

Rank #52 in the world

Tetris css battles

Rank #62 in the world

Tetris css battles

Rank #86 in the world

Tetris css battles

Rank #74 in the world

490 total public github contributions in the last year

Midjourney

Midjourney

Software engineer, February 2025 - Now Work
  • Adding ability to have multiple layers and rotate layers in the editor on the website
    • This required a full refactor of the editor to be able to adapt to the new features
    • Redesigned the entire editor to work better with the new tools
  • Owned the social profiles feature. A tweet about it
    • A full new profile page with profile settings and customizability
    • Adding the ability to follow other users
    • Adding a new interaction called "Spotlighting" that lets users highlight the favorite creations
  • Added a popup that showed when users ran out of credits that let them buy new ones or upgrade plan very easily. This popup alone paid for my salary within a couple of weeks

JmailJmail, JeffTubeJmail, JCalJmail

February 2026 - Now Sideproject

Jmail is a project maintained by a group of self-organized hackers in the SF area and its goal is to build a platform to make it accessible to learn about the Jeffrey Epstein case. I built and scraped all the data for JeffTube on my own initially, and right after launch it got integrated into the Jmail organization where I helped out on the main platform. I later built the entire frontend for JCal which shows a calendar of all the events related to the case.


  • JeffTube got over 150k likes and over 10 million views on twitter in total, here are some tweets here and here
  • Videos on JeffTube have gotten over 13 million views
  • Jmail has gotten over 150 million views and has been featured in many news outlets and online
Jmail
JeffTube
JCal
JmailJmail
Profile
Compose
Inbox
7460
Starred10550
Unredaction
Sent4295
Attachments
Daily Activity
Topics
Asking for advice
Introductions
Damage control
Conspiring w/ Brunel
✨AI Overview

You are logged in as Jeffrey Epstein. These are real emails released by Congress. Explore by name, search, visit a random page, or vote for an unredaction.

Random Page
All accounts ▾
Old releases ▾
Date ▾
1-100 of 7499
Primary
Promotions6104 new
732
191
cody rudland
Yahoo
You are dead- Lol good riddance
Aug 13, 2019
406
204
Cecilia Steen
Yahoo
With love- My dearest Jeffrey, I don't know when you'll get to read this...
Jul 25, 2019
828
Flipboard 10 for Today
11 questions for Mueller- Flipboard Interesting stories worth your time.
Jul 13, 2019
637
Flipboard Week in Review
Alex Acosta resigns, Jeffrey Epstein arrested- and Trump ends bid for citizenship question...
Jul 13, 2019
480
201
- Dear Jeff, I read the news papers today, I can't believe they arrested you again
Jul 10, 2019
250
Intelligence Squared
John Humphrys: The Terrier of Today- in conversation with Justin Webb
Jul 9, 2019
196
conchita sarnoff
Yahoo
Private & Confidential- Hello Jeffrey, I've been giving much more thought...
Jul 7, 2019
188
conchita sarnoff
Yahoo
Private and Confidential- Hello Jeffrey, In light of what has occurred...
Jul 7, 2019
201
Flipboard Week in Review
U.S. celebrates Fourth of July- Trump-Kim DMZ meeting and Hong Kong protests
Jul 6, 2019
1134
655
Weingarten, Reid 8
Re:- Charged criminally in sdny...Lithuanian hottie...
Jul 6, 2019
JeffTubeJeffTube
Profile
Home
Shorts
Explore more
Banner
Jeffrey Epstein
Jeffrey Epstein
@jeevacation · 1102 videos · 9,496,123 views · 68,056 likes
All of the videos released by the DOJ from the Epstein files.
Videos
Playlists
0:01
EFTA01648780.mp4
771.9K views · 3.3K likes
0:58
EFTA01648923.mp4
525.1K views · 5.1K likes
0:02
EFTA01648735.mp4
473K views · 781 likes
0:36
EFTA01683436.mp4
388.2K views · 838 likes
0:14
EFTA01648901.mp4
312.5K views · 1.2K likes
1:23
EFTA01683147.mp4
298.7K views · 2.1K likes
0:08
EFTA01683512.mp4
245.1K views · 654 likes
0:45
EFTA01648799.mp4
219.3K views · 491 likes
JCalJCal
Profile
July 2014
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Dec 2006 – Jan 2007
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Sarah Kellen, Nadia Marcink...
Sergey's Departure
Deliver up-to-date budget of the office building
Lunch with Anne and Sergey
Visit from Sergey Brin in St. Barth's
Call Gmax
Gmax's Departure from St T
Company update polaroid

Dema.ai

Software engineer, April 2023 - February 2025 Work

  • Full-stack ownership of the web-app (core product).
    • Owned internal state management with Jotai
    • Led and developed a Product Segmentation feature on my own that single-handedly secured multiple clients. This feature handles and labels tens-of-thousands of products per day. See it here
    • Developed our Marketing Mix Model feature on the application side. See it here
    • Migrated legacy SASS components to custom Chakra UI (moral of the story, chakra is a mistake, just use tailwind)
    • Worked on dashboards
    • Worked on teams and role-based access control
  • Owned and wrote almost all of the changelogs, See it here
  • Built our Shopify integration handling all order and inventory data for our Shopify customers. Later, I created a monorepo for all our other e-commerce integrations, saving multiple hours of dev-time for our engineers. Used Turborepo and deployed it to K8s
  • Bought a Polaroid camera on my very first day, which has taken well over 300 pictures and has been a core part of the internal employee branding. I also took it one step further on my 1-year anniversary and created a custom page with all Polaroids. See it here
Live site

Dema is an analytics platform for e-commerce that helps companies understand their profitability. It's a very cool platform and down below is a small replica to showcase sort of how it looks but also some things you can do. Of course there is A LOT more to the platform than what is down below:)

Dashboard
Reports

Starting view

Show compare

Channel
Channel group
Visits
Sales
Instagram
Meta

7,645

17.62%

567

18.37%

Facebook
Meta

5,123

6.73%

423

5.49%

Google Ads
Google

3,137

8.17%

289

17.96%

YouTube
Google

2,123

17.94%

178

14.10%

TikTok
ByteDance

4,567

42.72%

345

20.21%

LinkedIn
Microsoft

1,567

11.93%

134

19.64%

Twitter
Twitter

2,567

11.61%

201

6.35%

Pinterest
Pinterest

1,267

15.18%

98

15.29%

Snapchat
Snap Inc.

3,567

15.06%

267

14.10%

Email
Direct

4,567

8.74%

389

9.27%

Organic Search
SEO

6,567

13.22%

512

7.11%

WhatsApp
Meta

2,345

11.67%

187

13.33%

Bing Ads
Microsoft

987

16.12%

76

22.58%

Reddit
Reddit

1,876

17.25%

143

11.72%

Quora
Quora

765

9.29%

54

12.50%

Display Ads
Google

3,456

8.00%

278

9.45%

Affiliate
Partners

2,345

17.25%

198

12.50%

Referral
Partnerships

1,234

12.18%

98

12.64%

Direct
Direct

5,678

9.19%

467

10.40%

Podcast Ads
Audio

876

16.80%

65

20.37%

SMS
Direct

1,543

10.21%

132

11.86%

Push Notifications
Mobile

2,109

11.00%

176

10.69%

Webinars
Events

987

16.12%

87

19.18%

Lovable

Part-time consultant, November 2024 Work


Built their landing page over a couple days while I was solo traveling in Thailand. This was part of their rebrand for their third launch, which happened to make them the fastest growing company in Europe ever.

Lovable profile image

Lovable

@lovable_dev

Building products takes too long. We started Lovable to fix this.

Today, we`'re officially launching the world`'s first AI Full Stack Engineer

Lovable reliably replicates the capabilities of a full stack engineer and handles everything from design to database operations by integrating with Supabase.

So what`'s new exactly? 🧵
73
142
642
759

Codex fork

March 2026 Sideproject

I forked OpenAI's Codex CLI and added different games to it that would play while you agent was running. You could play, Tetris, Flappy Bird, Wordle, Subway surfers, snake and Connect 4
My tweet
Repository
codex — ~/Desktop/codex/codex-rs — 80×24
model: gpt-5.3-codex high/model to changedirectory: ~/Desktop/codex/codex-rs

Tip: this is an interactive demo, click on the tetris game and use the arrows to play!

● Fix all bugs ever!

Tetris
Arrows: move  Up/Space: rotate  Enter: drop
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● Planning sequential command execution(19s ● esc to interrupt)·1 background terminal running·/ps to view·/clean to close
gpt-5.3-codex high · 18% left · ~/Desktop/codex/codex-rs

CSS only Rubik's cube

October 2022 Sideproject

The project below was made with a total of ZERO lines of Javascript, it's all just CSS. Every animation, hover effect and button click is just a combination of some clever CSS code.

I made this because a friend told me it was not possible to do, so out of spite, I had to prove him wrong. That's also why if you look very closely in the background of the real website there are a lot of "L"s in the background
Repository
Live site

Professional Overwatch Player Overwatch

2017 - 2020 Sideproject

  • I was consistently in the top #500 rankings for europe on playstation with multiple different accounts, peaking at top #30 at points.
  • Competed for the scandinavian team in the world cups for Playstation
  • For certain heroes I was in the top #100 for and peaked #7 for Winston at a certain point.
  • I was 13-16 years old btw

Spotilist

March 2024, Sideproject

I absolutely love music and listen to it all the time. I get over 100,000 minutes on my Spotify Wrapped, but I did not want to wait until the end of the year to see what I enjoy listening to, so I reverse-engineered the Spotify API to get my listening stats and display them on a website.
Live Site
GitHub

Daij

March 2026, Sideproject

I used Strudel to generate the music via each of the 3 big models via their CLI. Then I made a website where users can listen to all the songs and vote to determine the best LLM for music taste.
Live Site
GitHub

ANTHROPIC

Claude

Claude

OPENAI

ChatGPT

ChatGPT

GOOGLE

Gemini

Gemini

Top songs

Midnight Ink
▶

Midnight Ink

Gemini

Dialogue in Felt and Skin
▶

Dialogue in Felt and Skin

Gemini

Blue Salon Waltz
▶

Blue Salon Waltz

ChatGPT

Solstice Carousel
▶

Solstice Carousel

ChatGPT

Dark Roller
▶

Dark Roller

Claude

Mouth Music
▶

Mouth Music

Claude

Pixel Quest
▶

Pixel Quest

Claude

Quest for the Golden Pixel
▶

Quest for the Golden Pixel

Gemini

CSS Sudoku

December 2025, Sideproject

Fully functional game of sudoku, made only with CSS, no javascript. Cuz I felt like it :)
Live Site
GitHub
Easy mode
Number pad

Vercel UI

Creator and sole maintainer, 2024 Sideproject

Design library inspired by Vercel's design system. It's the same concept as ShadcnUI but does tackle some issues I felt ShadcnUI skips over, like handling multi-part components with multiple different sizes for example.
Repository Live site
graygray-subtlebluepink-subtlegreengreen-subtletealteal-subtleblue-subtlepurplepurple-subtlegraygray-subtleblueblue-subtlepurplepurple-subtleamberamber-subtleredred-subtlepinkamberamber-subtleredred-subtlepinkpink-subtlegreengreen-subtletealteal-subtle
npm init next-app
Blue
Matheus
Is this red?
Vaaarning
npm init next-app
npm init next-app
Blue
Matheus
Is this red?
Vaaarning
npm init next-app
npm init next-app
Blue
Matheus
Is this red?
Vaaarning
npm init next-app

Acasting.se

First software engineer, part-time consultant, November 2023 - March 2024 Work

  • Built out the entire app, end to end, together with another engineer, and launched the first version in a single month
  • Scaled from 0 to 20k users
  • Was involved in all technical decisions
  • Handled billions of row reads, and millions of row writes
  • Developed a custom in-house chat to reduce our monthly costs by over $500/month
  • Worked on our recommendation engine
  • Implemented mobile design and responsiveness
  • Introduced our location feature, helping 100s of casters find amongst 1000+ locations (very similar to Airbnb)
Live site

LucioCode

April - March 2021 Sideproject

TLDR; It's Leetcode and CSS battles combined into one that I made in early 2021 for fun. This project also landed me my first job as a software engineer, so it holds a special place in my heart.
Repository
Live site

Simple addition

Easy

Given two integers, a and b, return the sum of a + b

Sample Input

a = 5 
b = 7

Sample Output

12

Explanation

The sum of of 5 + 7 is 12

Polaroid arrow
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