docs(index): update documentation content and structure

docs/content/docs/index.mdx

@@ -1,31 +1,68 @@
 ---
-title: Hello World
+title: Introduction
-description: A Fumapress site styled with shadcn/typeset
+description: Prad's Random CS Notes
 ---
 
 ## Overview
 
-This page renders through Fumadocs MDX and is styled by the `typeset typeset-docs` container — headings, paragraphs, lists, tables, and code all inherit their rhythm from three variables: `--typeset-size`, `--typeset-leading`, and `--typeset-flow`.
+This is a collection of random CS notes that I've made over the years. I've been learning CS for a while now and I thought it would be a good idea to make a public repository of my notes. This is the first iteration of the repository and I plan to add more content to it over time.
 
-### Why one CSS file?
+## The Golden Rule (Memorize This)
 
-- The file lives in your repo — edit rules directly, no plugin config
+**Only sort if the problem asks for ORDER or RANKING.**
-- Spacing flows one direction (`margin-block-start` only), so streamed content never restyles earlier blocks
-- Zero-specificity `:where()` guards mean Tailwind utilities always win
 
-```ts
+If the problem asks for:
-// Inline overrides still work inside a typeset container
+- "first"
-export const rhythm = {
+- "index"
-  size: "15px",
+- "position"
-  leading: 1.75,
+- "does it exist"
-  flow: "1.5em",
+- "true/false"
-};
+- "count how many"
-```
+
+→ **DO NOT SORT**. Just use the frequency map and loop.
+
+---
+
+## Decision Cheat Sheet
+
+| What the problem wants                  | Do you need to sort? | What to do instead                  | Example Problem     |
+|-----------------------------------------|----------------------|-------------------------------------|---------------------|
+| Sort characters by how often they appear | YES                 | Freq + Sort                         | LC 451             |
+| Top K most frequent                     | YES                 | Freq + Sort + slice                 | LC 347             |
+| Sort array by frequency                 | YES                 | Freq + Sort                         | LC 1636            |
+| First unique character (index)          | NO                  | Freq + loop original string         | LC 387             |
+| Is it an anagram?                       | NO                  | Freq + check counts                 | LC 242             |
+| How many numbers smaller than current   | Kind of             | Freq + prefix count                 | LC 1365            |
+| Most frequent element                   | NO                  | Freq + find max                     | LC 169             |
+
+---
+
+## Mental Checklist (Say this out loud every time)
+
+1. "Did I count the frequencies?" → Yes
+2. "Does the problem care about the **original order**?"  
+   - Yes → Loop the original string/array and check freq
+   - No  → You can sort
+3. "Does it want an **index** or a **boolean**?"  
+   - Yes → Almost never sort
+4. "Does it want the elements **re-ordered**?"  
+   - Yes → Sort by frequency
+
+---
+
+## Super Short Version to Tattoo in Your Brain
+
+**"If it wants the first / index / true-false → loop original.  
+If it wants sorted / top k / reordered → sort."**
+
+---
+
+## Practice Trigger Words
+
+- "first non-repeating" → Loop original
+- "return its index" → Loop original  
+- "sort by frequency" → Sort
+- "top k frequent" → Sort + slice
+- "valid anagram" → Just check counts
 
-> Tune a tighter preset for chat, a roomier one for docs — same file, different rhythm.
 
-| Control            | Purpose               | Default  |
-| ------------------ | --------------------- | -------- |
-| `--typeset-size`   | Base text size        | `1em`    |
-| `--typeset-leading`| Line height           | `1.75`   |
-| `--typeset-flow`   | Space between blocks  | `1.25em` |