diff --git a/shared/challenges_markdown/three/part_one.md b/shared/challenges_markdown/three/part_one.md
index d2d534e..147bc11 100644
--- a/shared/challenges_markdown/three/part_one.md
+++ b/shared/challenges_markdown/three/part_one.md
@@ -1,43 +1,101 @@
-To recap: [records](https://atproto.com/guides/glossary#record) are kept in [repo](https://atproto.com/guides/glossary#data-repo)s on [PDS](https://atproto.com/guides/glossary#pds-personal-data-server)es.
+# Test-drive a CAR
 
-**Today we're looking at the repo!** Or at least its serialized format.
+When apps sync data from your PDS, it comes in a format called a [**C**ontent **A**ddressable a**R**chive](https://ipld.io/specs/transport/car/carv1/#format-description): a CAR file! 🚗
 
-The repo (repository) is a key-value store of repo-keys to records. The data structure used is called a Merkle Search Tree (MST), but we're not going to worry about that just yet.
+This archive can contain your entire "repo" (repository), which is your **[records](https://atproto.com/guides/glossary#record)**, their **keys** (the record's `collection` and `rkey` combined). <small>It also has some additional structural info [for the MST](https://atproto.com/guides/data-repos#data-layout), but we're not going to worry about that just yet!</small>
 
-Wait, "repo keys"?? Remember [yesterday](./2) how an at-uri is made of three parts, `at://<did>/<collection>/<rkey>`? The second two parts together, `<collection>/<rkey>`, make up the actual raw keys (repo keys) inside your atproto repository.
+## YOU WOULDN'T DOWNLOAD A CAR
 
+&hellip;who are we kidding,
 
+<a id="download-car" href="" class="btn btn-primary btn-disabled">Loading (JS required) &hellip;</a>
 
-TODO blah blah merkle tree but not getting too distracted because this is about the CAR
-
-where do CARs come in?
-
-- nice neat serialization format
-- what you get when you export your repo
-- what apps get when they sync your repo
-- what PDSs send as proof for sync.getRecord
-- what gets sent over the firehose
-
-- header with root cid
-- blocks (cid, block)
-
-- block content is dag-cbor (already covered a bit from day 2)
-- there are also MST blocks (also dag-cbor, you can ignore them if you want)
-
-OH YEAH terminology note: dag-cbor is out, i think we're all drisl now? drisl-cbor?
-
-- CIDs (ignorable)
-
-### Your CAR is ready
-
-Click the button below for your very own CAR export of an atproto repository. Search the CAR for your verification code and submit it below.
+Your challenge: **find the `verification_code` hidden inside**.
+
+<details>
+  <summary>Hint: atproto CAR tools (easy-mode)</summary>
+
+  There are some nice web tools for poking around in a CAR:
+
+  <ul>
+    <li>
+      <a href="https://satnav.rsky.dev/" target="_blank">
+        Satnav
+      </a> from Blacksy
+    </li>
+    <li>
+      <a href="https://boat.kelinci.net/repo-archive-explore" target="_blank">
+        Archive explore
+      </a> on boat.kelinci.net
+    </li>
+    <li>
+      <a href="https://pdsls.dev/car/explore" target="_blank">
+        Explore archive
+      </a> at PDSls
+    </li>
+  </ul>
+
+  Or, if you have the [goat](https://github.com/bluesky-social/goat?tab=readme-ov-file#goat-go-at-protocol-cli-tool) command-line utility installed, try running:
+
+
+  ```bash
+  goat repo --help
+  ```
+
+</details>
+
+<details>
+  <summary>CAR libraries (write some code)</summary>
+
+  If you're feeling adventurous, you can write a program to show the contents of a CAR file. Some libraries that can help:
+
+  <ul>
+    <li>
+      <strong>python:</strong>
+      <a href="https://atproto.blue/en/latest/atproto/atproto_core.car.car.html" target="blank"><code>atproto_core.car</code></a>
+      (has sample code)
+    </li>
+    <li>
+      <strong>javascript:</strong>
+      <a href="https://github.com/mary-ext/atcute/tree/trunk/packages/utilities/repo" target="blank"><code>@atcute/repo</code></a>
+      (advanced)
+    </li>
+    <li>
+      <strong>golang:</strong>
+      <a href="https://pkg.go.dev/github.com/bluesky-social/indigo@v0.0.0-20260318212431-cbaa83aee9dd/atproto/repo" target="blank"><code>indigo/atproto/repo</code></a>
+      (advanced)
+    </li>
+    <li>
+      <strong>rust:</strong>
+      <a href="https://docs.rs/jacquard-repo/latest/jacquard_repo/index.html" target="blank"><code>jacquard_repo</code></a>
+      (advanced)
+    </li>
+  </ul>
+</details>
+
+<details>
+  <summary>Binary spelunking (bits &amp; bytes)</summary>
+
+  Oh, you want hard-mode? Here:
+
+  - [CAR format spec](https://ipld.io/specs/transport/car/carv1/#format-description)
+  - [MST atproto spec](https://atproto.com/specs/repository#mst-structure)
+
+  <details>
+    <summary>Binary <span style="text-decoration: line-through">hint</span> cheat</summary>
+
+  Text inside records is not compressed or weirdly encoded, and CAR just length-prefixes blocks without changing any bytes, so `strings` or even `hexdump -C` on your CAR might be worth trying&hellip;
+  </details>
+
+</details>
 
-<a id="download-car" href="" class="btn btn-primary btn-disabled">Loading (JS required) &hellip;</a>
 
 <script>
+console.log("?????");
 (function() {
   const button = document.getElementById('download-car');
-  const carData = atob("{{car_base64}}");
+  console.log("{{{car_base64}}}");
+  const carData = atob("{{{car_base64}}}");
 
   if (carData.length === 0) {
     button.textContent = 'Log in to download';
@@ -45,7 +103,7 @@ Click the button below for your very own CAR export of an atproto repository. Se
   }
 
   button.classList.remove('btn-disabled');
-  button.textContent = 'Download your CAR file';
+  button.textContent = 'Download a CAR';
 
   const bytes = new Uint8Array(carData.length);
   for (let i = 0; i < carData.length; i++) bytes[i] = carData.charCodeAt(i);