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Simon Lou

@simonlou.com
46 followers 162 following 50 posts

User Interface Designer & Typography Enthusiast Currently Building the Mac app @usebilly.app simonlou.com

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Simon Lou @simonlou.com · 24/09/2026
I noticed the same phenomenon when designing my app @usebilly.app – back then for Tahoe. After that realization, I sketched up an OS X Leopard version and worked back from that to distill what was good then and bring it back to the future. 2 of 2
Billy app in OS X Leopard style.
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Simon Lou @simonlou.com · 24/09/2026
Brent makes an interesting subpoint, or maybe it’s just what I read into it. He tried to improve NetNewsWire for Golden Gate and it felt “old” to some. 1 of 2
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Simon Lou @simonlou.com · 11/09/2026
As soon as Apple approves the update Billy will be able to create quotes!
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Simon Lou @simonlou.com · 04/09/2026
Billy doesn’t do the full tax side—real ElStEr filing needs Elster’s certified ERiC software, and a UStVA also pulls from your expenses, which Billy doesn’t track. The revenue side is what Billy knows. I could build a plugin that reads your invoices and calculates the numbers to type into ELSTER.
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Simon Lou @simonlou.com · 01/09/2026
Currently working on an expansion for the plugin system inside @usebilly.app to let you build plugins that can connect to other apps and modify your invoices. For example, it would be possible to automatically mark invoices as paid based on your bank transactions. #indiedev #macos #BuildInPublic
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Simon Lou @simonlou.com · 31/08/2026
It’s an honor to see my app featured here!
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Simon Lou @simonlou.com · 20/08/2026
Thank you Alex (@iphoneblog.de), for your kind words about my app (@usebilly.app) on the @bitsundso.de podcast. I was happy when I found it. www.bitsundso.de/bus1019 (German)
bitsundso.de
Bits und so #1019 (Der Geld-Ring) | Bits und so
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Simon Lou @simonlou.com · 04/08/2026
Nice to see that the skill of people like @lmnt.me still gets recognized while most are on a very different design path currently.
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Simon Lou @simonlou.com · 30/07/2026
Sounds smart to keep in mind, but at the same time it really is the edge-case of an edge-case.
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Simon Lou @simonlou.com · 30/07/2026
I can tell you, getting the layout breaks in @usebilly.app right took a lot of time and sweat.
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Simon Lou @simonlou.com · 30/07/2026
Yes, I think so too. Line items should always stay whole—can be really confusing otherwise.
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Simon Lou @simonlou.com · 29/07/2026
Found a place for the barber pole progress bar! @marioguzman.bsky.social
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Billy @usebilly.app · 28/07/2026
Somehow I forgot to introduce Billy version 1.1 here! It’s out of beta since last week with some highly requested features like multi-page invoices, markdown formatting, and support for the US Letter format. #indiedev #macos #BuildInPublic
Illustration of three new features: Multi-Page Support, Document Formats, Markdown Formatting
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Simon Lou @simonlou.com · 25/07/2026
@usebilly.app is now also available for download via Homebrew!
Merged pull request for "billy" version 1.1.1 in homebrew-cask repository
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Simon Lou @simonlou.com · 15/07/2026
Since when is Apple faster to approve production builds than a TestFlight builds? I even added the TestFlight one a little earlier. So I guess my new motto for the Beta is: Get the updates extra late!
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Billy @usebilly.app · 15/07/2026
We got featured! Thank you so much @lucas.love for the kind words. It’s great having you as such an invested user!
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Simon Lou @simonlou.com · 12/07/2026
Good interview! I’m always a fan of @meredithmeredith.bsky.social, but I like that it’s a little bit more in-depth—down to some technical details. youtu.be/aMNWOqXpxcc
youtu.be
AI’s Threat to Privacy - Signal President Meredith Whittaker on the Risks of Agents
YouTube video by Nicholas Thompson
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Simon Lou @simonlou.com · 04/07/2026
It’s Christmas! Thank you so much @marioguzman.bsky.social—that’s so sweet of you. <3
A handwritten note is displayed inside a holiday card, alongside a one-dollar Steve Jobs coin.
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Billy @usebilly.app · 26/06/2026
A lot of people still write their invoices in Pages, or even InDesign—so did I. Most accounting tools out there are web-based, expensive, and keep your data hostage. Pages works, but was never meant for this, and that makes it easy to mess simple things up. #indiedev #macos #BuildInPublic
The left side of the screen displays icons for Pages, Figma, InDesign, and Word. An arrow points from these icons to the Billy icon on the right side.
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Simon Lou @simonlou.com · 26/06/2026
Happy to hear that! Thank you. I’m doing my very best to build something that is truly useful, in the spirit of the Mac, and have some fun along the way.
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Simon Lou @simonlou.com · 26/06/2026
Very grateful to see my app @usebilly.app featured in the Piccalilli newsletter. Thanks, @bell.bz!
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Simon Lou @simonlou.com · 18/06/2026
Glad to hear anyway. Maybe some day.
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Simon Lou @simonlou.com · 16/06/2026
I would really appreciate any feedback on functionality, the feature set as well as the visual design of the app.
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Simon Lou @simonlou.com · 16/06/2026
You can just download the app for free to test all functions and see if it’s for you. A license is only required as soon as you start exporting invoices. If you want to test the different export formats as well, just send me an email—I’m happy to provide a free license for a month.
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Simon Lou @simonlou.com · 16/06/2026
We are live! I’m really happy to tell you that Billy is now available for download in the Mac App Store and directly from my website. usebilly.app/download apps.apple.com/app/billy-in... #indiedev #macos #BuildInPublic
An image introducing the app Billy showing its app icon with a sticker reading “Beautiful Bureaucracy” and confetti in the background.
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Simon Lou @simonlou.com · 15/06/2026
When the circular toolbar buttons are not concentric anymore with the window corner anyway, why can’t we have rounded rectangular buttons back? Like this, it’s much less space-efficient and looks worse. Isn’t a rectangle just the superior shape for a button? #macos #macos27
A screenshot showing the macOS Golden Gate Finder toolbar.
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Simon Lou @simonlou.com · 15/06/2026
Yay, Apple wants us! I guess the launch will happen tomorrow then!
A notification indicating that “Billy – Invoice Manager“ version 1.0.0 has been approved by App Review.
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Simon Lou @simonlou.com · 02/05/2026
Since I live in Germany, my first priority was to comply with the local regulations, but I’m open to supporting more countries. If you have specific needs for your place of residence, don’t hesitate to request a feature or get in touch. I will do my best to implement the requested features quickly.
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Simon Lou @simonlou.com · 02/05/2026
Your friendly neighborhood invoice manager has arrived! Beta access is now open! testflight.apple.com/join/aCCf242f
A graphic introducing “Billy,” an e-invoicing Mac app in open beta.
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Simon Lou @simonlou.com · 24/04/2026
Follow @usebilly.app for more info in the future.
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Simon Lou @simonlou.com · 24/04/2026
I’ve been working on my first Mac app for a while now, and it’s finally coming out next week. It’s an invoicing app for freelancers called “Billy”—creating, managing, and customizing e-invoices. Everything done locally and natively. #indiedev #macosdev #buildinpublic
Announcement poster of the app “Billy”. Open Beta on May 1, 2026.
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Simon Lou @simonlou.com · 06/11/2025
Great talk.
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Simon Lou @simonlou.com · 06/11/2025
Why did I think @bradfrost.com would speak about design or development or so? Anyway, I guess I was wrong.
Brad Frost on stage playing bass
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Simon Lou @simonlou.com · 14/09/2025
I stumbled upon this very elegant way of gender-neutralizing words in German using a version of an asterisk which fills the whole x-height. It would be fantastic if type designers would begin incorporating such a glyph into their fonts.
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Schöpflin Stiftung @schoepflinstiftung.bsky.social · 29/07/2025
Gemeinsam mit Publix und @algorithmwatch.org laden wir ein zum Gespräch mit @meredithmeredith.bsky.social, Präsidentin des Messengers Signal, über die Frage, wie wir Technologie wieder stärker an menschlichen Bedürfnissen ausrichten können – vor allem beim Schutz unserer Privatsphäre. ➡️ t.ly/lIzA3
Das Individuum in der Maschine: Meredith Whittaker über die Rückgewinnung der Privatsphäre im Zeitalter der KI
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Simon Lou @simonlou.com · 01/07/2025
A = Like B = Favorite C = Bookmark
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Simon Lou @simonlou.com · 01/07/2025
If you’re up for the challenge:
I converted an old 5K iMac to a monitor—that worked well and is a nice way to save an old device from the scrapyard. Also nice to save some money—you can find a 5K iMac for 300€ and could even sell the internals afterwards, cause you’ll only need display and housing.
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Simon Lou @simonlou.com · 23/06/2025
Did they wrote by mistake “Version 16.0” in the first beta? :D
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Simon Lou @simonlou.com · 17/06/2025
Always nice to read.
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Simon Lou @simonlou.com · 13/06/2025
I was wondering when this post would come.
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Simon Lou @simonlou.com · 10/06/2025
Ouuh, that’s very nice! I guess we have to celebrate the little things.
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Simon Lou @simonlou.com · 10/06/2025
I kind of like the new cursor.
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Simon Lou @simonlou.com · 10/06/2025
That is so sad! It made me really happy to see well crafted Mac icons with clever ways to keep the squircle while having some elements overlap the edge.
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kepano @stephango.com · 09/06/2025
a few well-chosen typos relaly make your prose seem like it wasn't written by AI
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Simon Lou @simonlou.com · 09/06/2025
Some of the glassy, floating elements look really beautiful (e.g. in Maps), but for example the floating toolbar seems so out of place in most Mac apps. #macos26
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Simon Lou @simonlou.com · 09/06/2025
I don’t know, but the corner radius feels just wrong. #wwdc25 #macos26
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Simon Lou @simonlou.com · 09/06/2025
Welcome I guess #wwdc25 #macos26
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The Iconfactory @iconfactory.iconfactory.world.ap.brid.gy · 09/06/2025
Looks like we were ahead of the clear icon curve all the way back in 2006! 😉 #WWDC freeware.iconfactory.com/preview/cl…
Clear finder Icons for the Mac desktop from 2006 including a clear hard drive, iCloud Drive and trash folder.
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Simon Lou @simonlou.com · 06/06/2025
The @letterformarchive.org is always a nice place to browse. :)
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