Aramis Lopez

RentRadar watches rental listings in New York, San Francisco, Los Angeles, Washington, Miami, San Diego and Chicago, and emails renters as soon as something fits their budget and taste.

I prototyped it with scrapers, then rebuilt it on licensed API data (RentCast, with HUD and Census context) because the big listing sites forbid scraping. The rebuild also let it run entirely on Cloudflare's free tier.

Stack

Next.js 15, React 19, OpenNext on Cloudflare Workers, D1, Stripe, magic-link sign-in, Resend

Hosting cost

$0 a month

Built

June 2026

Open RentRadar

Diurna publishes itself. Tuesday to Saturday it writes a morning brief on the previous session, Sunday a week in review, Monday a long-form theme, plus a chart of the day drawn from 29 FRED series and an economic calendar assembled from BLS, BEA and Federal Reserve schedules.

The rule that matters most: if an official source is down, it publishes nothing rather than stale numbers.

Data

FRED, U.S. Treasury, ECB, exchange closes

Runs

Four times a day on GitHub Actions

Commits

8 by hand · 46 automated

Code

3,783 lines, zero dependencies

Revenue

Display advertising

Read today's edition

A studio brand selling premium websites to New York restaurants, clinics, firms and shops. To show range before the first client, I designed and built six demo sites for different trades, each with its own identity.

Demo builds

Restaurant, med spa, law firm, gym, bakery, SaaS startup

Stack

Hand-written HTML, CSS and JavaScript on Cloudflare Pages

Built

July 2026

Visit the studio

Four estimation questions, word for word from Many Labs 1, the 2014 project that re-ran 13 psychology effects with more than 6,000 people. Each question opens with a number, and a coin flip on the server decides whether it is low or high. After the fourth answer the page reveals the trick and plots everyone's guesses live: low-anchor answers above the line, high-anchor answers below.

The design, exclusions, stopping rule and analysis were registered and archived before the first response. The analysis copies the original: answers outside the two anchors do not count, then a rank-based t-test and Cohen's d for each question, set against the published effects.

Status

Collecting: 0 of 200 counted, closes Nov 17, 2026

Registered

Archived Oct 3, 2026, before the first response

Stack

Cloudflare Pages Functions, D1, vanilla JavaScript and SVG

Commits

2 by hand

Code

1,452 lines

Read the pre-registration

The engine collects every posting from company job boards across 11 applicant-tracking systems, keeps business-side roles in the US or remote, then reads each full description and rejects anything that asks for more than two years.

It is the source FirstRung builds on, and it is tested like one: 438 automated tests cover the parsers, the experience gate and the ledgers that keep a role from ever being shown twice.

Commits

43 by hand · 52 automated

Code

21,351 lines of mostly Python

Schedule

Daily, unattended

Client acquisition for Mercer Studio. It pulls businesses that list an email but no website from OpenStreetMap across ten US metros, probes every domain and skips anyone whose site already works, then sends a capped, human-paced sequence.

At most 30 emails a weekday, 45 to 120 seconds apart, one follow-up after five days, and an inbox check first so nobody who replied gets a second note. Opt-outs are permanent.

Ran

July 2026, now paused

Commits

10 by hand · 17 automated

Code

453 lines of Python in one file

A bot for Kalshi's 15-minute Bitcoin up-or-down markets, 96 windows a day. Before risking money I backtested it across 1,319 windows. Every entry type lost money, and the calibration check showed why: the model was overconfident in every bucket.

Live trading stays locked behind an explicit override. Deciding not to ship it was the useful result.

Trades

1,188

Hit rate

39.2%

Expectancy

−8.52% per dollar staked

Max drawdown

$147.99 on $1,398.69 staked

Code

2,987 lines of Python

PolyWhale finds skilled Polymarket traders and flags the moments when several of them agree. Most of the work is deciding who to exclude. The top all-time wallet turned out to be a market maker with a −3.6% return on its positions, and 472 of 1,207 candidates were cut for the same reason.

Speed disqualifies too: copying a trader whose median hold is 3.6 hours with a 90-second poller only buys their exits. Sizing uses a quarter-Kelly stake, and on its first live cycle it correctly declined both signals it found because the price had already run.

• At least 25 closed positions
• Return on capital of 6% or more
• Volume no more than 40× profit
• Median hold of 6 hours or more
• No more than 55% of profit from one event
• At least 30% outside sports
• Traded within the last 10 days
• At least $5,000 at stake

Code

3,116 lines, standard library only

A native Android hydration tracker: an animated ring toward a daily goal, one-tap drinks, streaks, badges and weekly analytics. Kotlin with Jetpack Compose, Room for storage and DataStore for settings.

The signed release bundle and the Play Store assets are ready; the listing is next.

Stack

Kotlin, Jetpack Compose, Room, DataStore, AdMob

Code

2,136 lines

Built

April 2026

A calendar of the month with a list for every day. Finished tasks sink to the bottom, yesterday's leftovers come over with one click, repeats follow daily, weekday or weekly rules, and a streak only counts days that had something planned.

It runs on a laptop with no dependencies, or on Cloudflare Workers and D1 behind a password, with signed, sliding sessions and a throttled login. The theme builder shows live contrast ratios and can nudge an accent until it passes.

Themes

63, checked by 819 automated contrast tests

Stack

Vanilla JavaScript, Node, Cloudflare Workers, D1

Code

6,130 lines

Built

September 2026

Try the demo

A last-one-standing Roblox arena where tiles break under your feet. Players dash, fire shockwaves and charge a quake ultimate across seven escalating levels, with ranked trophies and a global leaderboard.

The whole world is generated from code at runtime, and the server is authoritative, so the client cannot fake a hit or a coin.

Code

4,576 lines of Luau across 24 files

Tooling

Rojo, luau-analyze, Roblox DataStores

Built

June 2026

A complete wedding planner in a single HTML file that works offline: budget tracker, guest list and RSVPs, drag-and-drop seating, vendor tracker, a twelve-month checklist and six themes. No install, no account, the data never leaves the couple's browser. I packaged it for Etsy.

A companion engine renders a 49-pin Pinterest library from HTML templates with headless Chrome and rotates it on a schedule with no repeats.

Planner

Vanilla JavaScript, fully offline

Pin engine

6 by hand · 1,704 lines of Python

Built

June 2026

See the planner