KHTDR – Apps

Zazen

mazzarelli@gmail.com (Joey Mazzarelli) — Sun, 27 Sep 2026 00:00:00 -0600

Zazen is a meditation timer for Android, and that is all it is. You pick a length, it gives you a few seconds to settle in, a bell starts the sit, a soft bed of noise plays underneath, and a bell ends it. There are no accounts, stats, streaks, or history, and it never nags you to sit.

Get the app

Android APK: Download Zazen 1.0.0 (~41 MB, Android 7.0 or newer, 64-bit phones)
Google Play: not published. This is a direct download.
iOS: not planned

Point your phone's camera at this to download the APK (~41 MB).

If you want to confirm the file you downloaded is the one I published, its SHA-256 is:

7dab571f7849620cac3079797371bc3d60fd4ad7416774b9b054f8b854fc499d

Install

Android only installs apps from the Play Store until you give permission, and you give it one app at a time.

Open the download link above on your phone.
When it finishes, tap the downloaded file. Android will say your browser (or file manager) isn't allowed to install unknown apps. Tap Settings, turn on Allow from this source, then go back.
Tap Install.
Play Protect may warn you that it doesn't recognize the developer. That's expected, because the app isn't in the Play Store. Tap More details, then Install anyway, if you're comfortable with that.

You can turn Allow from this source back off afterward. It isn't needed for updates.

Updates

Most updates arrive on their own. The app checks for one when it opens and downloads it in the background. The update takes effect the next time you open the app, never in the middle of a sit. You only need to download a new APK when the version number on this page changes. You can also check for an update yourself under settings → Updates.

How a sit goes

Pick a length. 5, 10, 20, or 30 minutes, or your own length from 1 to 120.
Settle in. The screen counts down a short pause (10 seconds unless you change it). Toward the end, a bowl sings as it's rubbed around its rim, so you already know the bell's pitch when it's struck.
The start bell. Once it has rung out, the bed of noise fades in.
Sit. If you like, a soft bell marks the halfway point, or every 5 or 10 minutes.
The end bell. The noise either settles down under the bell or fades out before it, so the bell rings alone.

You can cancel at any point, and the sounds fade out rather than cut off. The sit keeps time by the clock, not by counting seconds, so locking the phone or switching apps doesn't throw it off. The whole sit is scheduled the moment you tap, so you still hear the bells with the screen locked.

The sounds

I really built this to have a clean place to play with sound, and there are no recordings in it. Every sound is synthesized on the phone as it plays, using the Web Audio API (through react-native-audio-api).

The bells are built from a handful of sine waves, one for each ringing tone of a real bell, each fading at its own rate.
The rim is the same tones, plus a band of noise for the friction of the mallet going around the bowl.
The bed comes in three characters:
- drift: pink, green, and brown noise slowly moving around each other and across the stereo field, so it is never quite still. Underneath is an optional binaural beat, which you only hear with headphones.
- pink: plain pink noise, like steady rain.
- brown: plain brown noise, darker, closer to surf.

Nothing ever starts or stops at full volume. Every sound ramps in and out, because a click is the last thing you want to hear ten minutes into a sit.

Settings

A small settings dialog holds everything you can change:

the bells on or off, their volume, and the interval bells
the background noise on or off, its character, its volume, and the binaural beat
how the noise ends: settling under the end bell, or fading out before it
the settling-in pause: 5, 10, or 30 seconds
your own sit length
whether the app closes itself once the last sound fades

Privacy

Zazen doesn't know who you are and doesn't keep track of your sits. The only thing it saves is your settings, in a small file on your phone. There are no ads, no analytics, no crash reporting, and no notifications. The only thing it ever sends over the internet is the check for app updates.

The app is free. It has no paid features, and I have no plans to add any.

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Mood Ring

mazzarelli@gmail.com (Joey Mazzarelli) — Fri, 25 Sep 2026 00:00:00 -0600

Mood Ring is a small Android app for noticing how you've been feeling. Now and then it asks a quick question, it has a short check-in at the end of the day, and it offers an occasional questionnaire. Then it shows you how things change over time. I made it for a small circle of friends and family, so it is not in the Play Store.

Get the app

Android APK: Download Mood Ring 1.1.0 (~35 MB, Android 7.0 or newer, 64-bit phones)
Google Play: not published. This is a direct download.
iOS: not planned

Point your phone's camera at this to download the APK (~35 MB).

If you want to confirm the file you downloaded is the one I published, its SHA-256 is:

657e8c7e6182276d92c8102633e193578cd27967364cb8628ad919f55b877021

Install

1. Let your browser install apps

Android only installs apps from the Play Store until you give permission, and you give it one app at a time.

Open the download link above on your phone.
When it finishes, tap the downloaded file. Android will say your browser (or file manager) isn't allowed to install unknown apps. Tap Settings, turn on Allow from this source, then go back.
Tap Install.
Play Protect may warn you that it doesn't recognize the developer. That's expected, because the app isn't in the Play Store. Tap More details, then Install anyway, if you're comfortable with that.

You can turn Allow from this source back off afterward. It isn't needed for updates.

2. Let the reminders through

The first time you open Mood Ring, it asks to send notifications. Say yes, or it can't remind you to check in.

Many phones also shut down background apps to save battery, which can make reminders show up late or not at all. If your reminders don't arrive:

Open Android Settings → Apps → Mood Ring → Battery.
Choose Unrestricted (some phones call it Don't optimize).

Samsung, Xiaomi, OnePlus, Huawei, and some other brands add their own extra battery settings. dontkillmyapp.com has step-by-step instructions for each brand.

Updates

Most updates arrive on their own. The app checks for one when it opens and asks before it restarts to apply it. You only need to download a new APK when the version number on this page changes. You can see which version you have in the app under Settings → About Mood Ring.

Uninstalling

Uninstalling Mood Ring deletes everything you've entered in it, unless Android backup is on (see below). If you want to keep your history, use Export JSON or Export CSV under Settings → Your data first and save the file somewhere safe.

What it does

Quick nudges. A few times a day, at random times within hours you choose, it asks "how are you feeling right now?" Answering is one tap on a five-point scale from Awful to Great, plus an optional energy rating.
An end-of-day check-in. A mood for the day, an optional note, and any questions you've added yourself. For example, "Did you exercise?" (yes/no), "How well did you sleep?" (a 1–5 rating), or "How many coffees?" (a count).
Occasional questionnaires. Short, widely used screening questionnaires, each on a schedule you pick, such as every two weeks:
- GAD-7 (anxiety)
- PHQ-9 (depression)
- K10 (psychological distress)
- PSS-10 (stress)
- WHO-5 (wellbeing)
- UCLA 3-item (loneliness)
- Satisfaction With Life Scale
History. A calendar colored by mood, and each day's entries in detail.

The reminders are deliberately vague, like "How are you feeling right now?" or "How was today?" They never show a mood, a score, or the name of a questionnaire, because notifications can show up on your lock screen.

It is not a diagnosis

Mood Ring is not a diagnostic tool, and it doesn't replace professional care. The questionnaires are screening tools. If you're worried about how you've been feeling, a doctor or other health professional can help. The app has an If you need help now screen with crisis lines. It works offline. In the US, you can call or text 988 at any time.

Privacy

It stays on your phone. Everything you enter is saved in a database on your phone. There is no account to create and no server to sync to.
Nobody else sees it. There are no ads, no analytics, no crash reporting, and no third parties. The only thing the app ever sends over the internet is the check for app updates, and that check sends none of your data.
Your own Google backup. Android backs up app data to your own Google account, so your history can come back when you move to a new phone. If you'd rather it didn't, turn it off in Android Settings → Google → Backup. That setting applies to the whole phone.
You can take it with you, or delete it. Settings can export everything to a JSON or CSV file that you save wherever you want, or delete all of it from the phone.

The app is free. It has no paid features, and I have no plans to add any.

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The Well Rounded Climber

mazzarelli@gmail.com (Joey Mazzarelli) — Sun, 30 Aug 2026 00:00:00 -0600

The Well Rounded Climber (tWRC) is an Android climbing log that tracks habits instead of grades. A V4 at one gym is not a V4 at another, and it is not a V4 outside. The app measures two things that do transfer: how your difficulty is distributed, and how varied your style is.

Get the app

Android APK — Download the APK (v1.1.0, ~35 MB)
Google Play — not published; this is a direct download
iOS — not yet built

Point a phone at this to download the APK directly (~35 MB).

Install

Android blocks installs from outside the Play Store until you allow it, per-app:

Download the .apk above on the phone (or copy it over).
Tap it. Android will offer to let your browser or file manager install unknown apps — grant that, then tap the file again.
Play Protect may warn you it does not recognize the developer. It does not; I am not in the Play Store. Install anyway if you are comfortable with that.

After that, app updates arrive over the air on launch. You only need a new APK when the native side changes.

Why not grades?

Grades are the main way climbers talk about difficulty, but they are a weak training signal. They depend on the gym, the setter, and the style. Chasing them tends to push you toward the climbs you are already good at, one grade below your limit, on the wall angle you like.

So tWRC never asks what a route was graded. It asks two questions instead.

The Pyramid — are you distributing your effort?

Every climb gets self-classified into one of three personal buckets, defined against your ability today rather than any gym's scale:

Base — easy mileage. Volume, movement, warm-up.
Core — hard but doable. Your working level.
Stretch — at or past your limit. Projects.

A healthy season is pyramid-shaped: a lot of base, a solid core, a few stretch. The chart shows you the shape you actually climbed.

There is no score, no percentage, and no verdict. What you get is a named gap, where you sat, and one small suggestion you can go check:

Last session: 8 base, 13 core, 1 stretch. Your last 6 weeks run core-heavy.

Next session: pick two slab problems.

There is a subtlety here that took a rewrite to find. The bars are drawn from effort (attempts plus a completion bonus), but the judgement about which way your training leans is computed from plain counts — one climb, one climb. If the lean were scored on effort instead, a single twelve-attempt project would outweigh an eight-problem warm-up block, and every session where you genuinely projected would read as "top-heavy." Sandbagging would score better than trying hard, for the exact climber this app is for. Now a project is one climb, because it is one climb.

The Spiders — are you climbing everything?

Three radar charts, tagged in the moment on any climb:

Hold Type — crimp, sloper, pinch, jug, pocket, volume, crack
Wall Angle — slab, vertical, overhang, roof, arete, stem
Movement — dyno, static, mantle, compression, lock-off

Tags are not exclusive: one climb can be a crimpy overhanging lock-off, and it counts in all three webs. Spokes are a raw tally — every tagged climb counts once, whether you onsighted it or failed on it for fifteen attempts, because the question a web answers is "have you touched this?" and a climb answers that once.

The tally only becomes useful with a denominator, so the webs report in sentences:

You logged 4 slab problems in 90 days, out of 210 climbs.

"4 slab" reads as a preference. "4 out of 210" is a gap.

The taxonomy is yours

Those eighteen dimensions are a starting point, not a rule. Your gym does not set cracks? A crack spoke pinned at zero will read as a gap nobody can close, so turn it off. Add your own. Turning one back on restores its whole history; nothing is deleted when it is hidden.

Logging has to be fast or it doesn't happen

If logging is slow, you will not do it. The form is built to be quick:

Level picks the form. Base asks nothing but "how many." Core asks the result and offers a one-tap "battled it." Stretch — the only place a count actually matters — asks for attempts on a keypad. One form serves three very different climbers, and it adapts within a single session, which a global "advanced mode" toggle never could.
Tags carry over from your last climb within a session, so a session on the same wall is one tap per problem. They are not saved overnight — last night's overhang should not attach to tomorrow's slab session.
There is an end-of-session pass that shows today's untagged climbs with a few recallable chips, for when you were too pumped to tag at the time.
No modes, no onboarding questionnaire. Nothing to configure before you can log a climb.

Make it yours

Pick three colors — canvas, accent, and a chart seed — and the app derives its entire theme from them. Every text color is checked against every background it lands on and corrected until it clears WCAG AA contrast, including for bad picks. A bad color choice should not leave you stuck in an unreadable settings screen you cannot see.

No ads, no tracking, no paid features

The app is free. There are no ads, no tracking, and no paid features, and there are no plans to add any. Everything you log lives in a SQLite database on your phone — no account, no server, no sync, nothing to sign up for, and nothing leaves the device.

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pexro

mazzarelli@gmail.com (Joey Mazzarelli) — Mon, 13 Jul 2026 00:00:00 -0600

pexro (Personal EXercise ROutine) is a personal mobile app that runs and tracks exercise programs described by uploaded JSON. No workout is hard-coded — the app is a generic interpreter over a schema. Describe a routine once, upload it, and pexro guides you through each session and tracks your progress over time.

Get the app

Google Play — Download on Google Play (link coming soon)
Apple App Store — Download on the App Store (link coming soon)

Create your program with an LLM

pexro doesn't ship a fixed routine — it runs a JSON program file you upload. The easiest way to make one is to let a language model write it for you.

Open your LLM of choice (ChatGPT, Claude, Gemini, etc.).
Give it the following prompt (use the Copy button, then paste it into the chat):

I want you to build me a personal exercise program for a mobile app called pexro. First, read the authoring guide and JSON schema at https://khtdr.com/pexro/llm.txt and follow it exactly. Then ask me about my goals, experience level, available equipment, any injuries, and how many days per week I want to train — before writing anything. Finally, output a single valid JSON program file that conforms to the schema, inside a code block so I can copy it. I'll import it into pexro either by pasting the JSON straight from this chat or by saving it as a .json file, so make sure the whole program is in one self-contained block.

Answer the model's questions. It will hand back a JSON program.
Import it into pexro one of two ways:
- Paste from clipboard — copy the JSON out of the chat and paste it directly into pexro. No file needed.
- From a file — or save the output as a .json file on your device and upload that.
Either way, the app validates the program on import and shows a clear error if anything is off — fix and re-import.

That's it. Change your training later? Ask for new JSON and import it again — your logged history is kept separate and carries over.

For developers & LLMs

The full authoring guide, a complete example, and the machine-readable schema live in plain text:

Authoring guide (for LLMs): khtdr.com/pexro/llm.txt
JSON Schema (draft 2020-12): khtdr.com/pexro/schema.json

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