All docs
math
Eigenvalues of a Matrix
What eigenvalues actually mean, how to compute them by hand, and worked 2×2 and 3×3 examples.
overview
Getting Started
What this space is and how it's organized.
design
How to Write a design.md File
A detailed guide to authoring a design.md — the single source of truth for a product's visual and interaction system.
react
React Hooks Cheatsheet
Quick reference for the hooks I reach for most.
diy
DIY Projects: Build Something Yourself
You don't need to be a programmer to build real, working, genuinely useful things anymore. Here's the mindset, the toolbox, and a set of fun projects to build this weekend.
stats
Statistics — Complete Study Notes
Complete notes from the Inferential Statistics sessions — descriptive statistics, central tendency, dispersion, quartiles, IQR and box plots, with worked examples and industry applications.
aisearch
Problem Solving with AI: The State-Space Framework
Every classic AI problem — 8-puzzle, water jug, missionaries and cannibals, N-queens — is the same thing underneath: a state space you search. Here is the shared vocabulary, the search strategies, and how to pick one.
aisearch
State Space Search: Formulation, Trees vs Graphs, and Complexity
The formal five-part problem definition, why a small state space produces an infinite search tree, the difference between a node and a state, tree-search vs graph-search, and the completeness and complexity of every uninformed strategy.
agents
Agent Skills, SKILL.md, and AGENTS.md: an overview
What "skills" mean for AI coding agents, how SKILL.md and AGENTS.md differ, and when to reach for each.
math
Shortest Paths — Overview & Map
The shortest-path problem, the family of algorithms that solve it, and how to pick the right one.
diy
Build a Personal Dashboard You'll Actually Use
A one-screen dashboard — clock, weather, to-dos, and a daily quote — built by just chatting with Claude. No code, about ten minutes.
ux
Mental Models in UX
Users arrive with a belief about how your interface works, formed by every app they've used before. Good design matches that belief instead of fighting it.
psych
Psychology 101: A Map of How Minds Are Studied
What psychology actually is, the big schools of thought, the branches worth knowing, and how to read psychological claims without being fooled.
react
Figma to Tailwind: The Complete Conversion Workflow
How to turn a full Figma design into clean HTML + Tailwind CSS — reading Dev Mode, mapping tokens and Auto Layout to Tailwind, and a worked hero-section example with complete code.
python
Python Lists & Dicts: The Complete Guide
Everything about Python's two workhorse data structures — creating, indexing, slicing, every method, comprehensions, nesting, copying, performance, and the gotchas — with a runnable example for every concept.
stats
Statistics Foundations: Descriptive vs Inferential
The split between descriptive and inferential statistics, worked classification examples, and why it matters in industry — A/B testing, feature engineering and AI bias detection.
ml
Supervised Learning: Classification vs Regression
The fundamental split in supervised learning — predicting a number versus predicting a category — with the full algorithm taxonomy, how to tell which problem you have, and the workflow every model follows.
aisearch
The 8-Puzzle: Sliding Tiles, Solved with A*
The canonical AI search problem. State representation, the four operators, why half of all boards are unsolvable, the misplaced-tiles and Manhattan-distance heuristics, and a full A* implementation with a traced solution.
math
BFS — Shortest Path in Unweighted Graphs
Breadth-first search finds the fewest-hops path, and it's the foundation every weighted algorithm builds on.
agents
SKILL.md files: the format behind Claude Agent Skills
A deep dive into the SKILL.md format — YAML frontmatter fields, directory layout, bundled scripts, progressive disclosure, and invocation control, with copy-pasteable examples.
design
Dashboards: UI/UX & How They've Evolved
What a dashboard really is, the three types, how dashboard UX evolved from static reports to real-time products, and where it's heading next.
diy
Build & Share a Browser Mini-Game
Describe a game in plain English, and Google AI Studio builds a real, playable web game you can deploy and send to friends. The same path used to build a game on games.aathan.in.
ux
How Users Actually Behave
People don't read, they scan; they don't optimize, they satisfice; they ignore what looks like an ad and never open the manual. Design for the real user, not the ideal one.
psych
Cognitive Biases: The Predictable Bugs in Human Thinking
System 1 vs System 2, the heuristics that usually serve us well, and the systematic errors they produce — anchoring, availability, loss aversion, confirmation bias, and how to actually debias.
react
Figma to Code: Worked Examples (Navbar, Cards, Stats Grid)
Three complete Figma-to-Tailwind conversions — a responsive navbar, a pricing card, and a dashboard stats grid — each from inspector specs to final HTML, plus the AI-assisted workflow.
python
Python Tuples: The Complete Guide
Everything about Python tuples — creating (and the one-element comma trap), packing & unpacking, immutability, slicing, the two methods, named tuples, when to use a tuple vs a list — with a runnable example for each.
stats
Variable Types: The Full Taxonomy
Numerical vs categorical variables in full — discrete, continuous, nominal, ordinal, unstructured data — plus the two classification traps that catch everyone.
ml
Data Preprocessing for Machine Learning
Turning raw data into something a model accepts — splitting X and y, imputing missing values, one-hot and label encoding, the train/test split, and feature scaling — worked end to end on a real messy dataset.
aisearch
Tic-Tac-Toe: Minimax and Alpha-Beta Pruning
The classic two-player game as an AI problem — the game tree, why minimax guarantees perfect play, how alpha-beta pruning cuts the work by 90%, and a complete unbeatable player in Python.
math
Dijkstra's Algorithm
The workhorse of shortest-path finding on weighted graphs — how it works, why it's correct, and a full worked example.
agents
AGENTS.md files: the open convention for coding agents
A practical guide to AGENTS.md — the plain-Markdown, cross-tool file that tells coding agents how to build, test, and follow conventions in your repo, with a full example and monorepo nesting rules.
design
Dashboard Design Principles
The core rules of dashboard UX — glanceability, visual hierarchy, layout patterns, choosing the right chart, and using color and numbers with intent.
diy
Build a Telegram Bot That Pings You Daily
A bot that messages you a quote, reminder, or weather update every morning — created with Telegram's BotFather and a no-code Make automation. No server, no code.
ux
UX Laws & Cognitive Principles
The named psychological principles behind good interfaces — Hick's, Fitts's, Miller's, Jakob's, Zeigarnik, Peak–End and more — each with how to apply it and example UIs.
psych
Memory & Learning: How to Actually Make Things Stick
The three-stage memory model, why working memory is the bottleneck, the forgetting curve, and the two techniques with the strongest evidence in all of psychology — spacing and retrieval practice.
python
Python Sets: The Complete Guide
Everything about Python sets — creating them, why they're unordered and unique, add/update, the four ways to remove, all the set operations (union, intersection, difference), frozensets, and when to use a set instead of a list.
stats
Measures of Central Tendency: Mean, Median & Mode
Mean, median and mode — formulas, merits and demerits, which to use for missing values, what outliers destroy, and how skewness shifts the three apart.
ml
Linear Regression: From the Maths to scikit-learn
The foundational regression algorithm — the best-fit line derived by hand, reproduced in scikit-learn, then a full real-dataset workflow with train/test split, standardisation and test-set metrics.
aisearch
The Block World Problem: Planning with STRIPS
A robot arm stacking blocks — the problem that gave us predicate representation, the STRIPS planner, goal stacks, and the Sussman anomaly that broke naive planning for a decade.
math
Bidirectional Dijkstra
Search from both ends at once and meet in the middle — often dramatically faster for single-pair queries.
agents
Model Context Protocol (MCP)
The open standard that lets AI agents plug into tools and data — the "USB-C port for AI".
design
Dashboard Optimization: Tips & Tricks
Practical UX and performance techniques that make a dashboard feel fast, calm, and effortless — from skeleton loaders to server-side aggregation.
diy
Turn a Google Sheet Into a Phone App
Put your data in a spreadsheet, connect it to Glide, and get a real installable phone app — habit tracker, collection catalog, expense log — with zero code.
psych
Motivation & Habits: Why You Do What You Do (and How to Change It)
Intrinsic vs extrinsic motivation, what dopamine actually does, the cue–routine–reward loop, and the evidence-backed mechanics of building habits that survive contact with real life.
python
NumPy Basics: Arrays, Dimensions & Slicing
Getting started with NumPy — why arrays beat lists (with real speed and memory measurements), creating ndarrays, dimensions, dtypes, indexing and slicing in 1-D and 2-D, and the array-generating helpers.
stats
Measures of Dispersion: Range, Variance & Standard Deviation
Why the average alone is never enough — range, variance, standard deviation, the population vs sample (n-1) question, Excel walkthroughs, and the coefficient of variation.
ml
Regression Algorithms Beyond the Straight Line
Polynomial regression, Ridge, Lasso and ElasticNet regularisation, decision tree and random forest regressors, gradient boosting and SVR — what each fixes, when to use it, and the code.
aisearch
Missionaries and Cannibals: Search Under Constraints
Three missionaries, three cannibals, one two-seat boat. The state representation that makes it tractable, why 12 of the 32 states are illegal, the full 11-move solution traced, and working BFS code.
stats
Skewness & Kurtosis: The Shape of a Distribution
The third and fourth moments explained with graphs — every skewness type (right, left, symmetric) and kurtosis type (lepto, meso, platy), their formulas, how to read the numbers, and how to fix skewed data.
math
A* Search
Dijkstra plus a heuristic — the point-to-point pathfinder behind game AI and map routing.
agents
Retrieval-Augmented Generation (RAG)
Ground an LLM in your own data by retrieving relevant context and feeding it into the prompt — the standard cure for hallucination and stale knowledge.
design
Dashboards in the Wild: Best Examples
What to steal from the best real-world dashboards — Stripe, Linear, Vercel, Datadog, Grafana, Plausible and more — plus the anti-patterns to avoid.
diy
Build a Real Web App From a Single Prompt
Describe an app — with logins and a database — in plain English, and Lovable builds and deploys the whole thing. The most ambitious no-code project, still no code.
psych
Social Psychology: What Other People Do to Your Mind
Conformity, obedience, persuasion, and the attribution errors we all make — the classic experiments, what modern re-examination changed, and the defence kit.
python
Pandas Basics: Series, DataFrames & Data Cleaning
A complete introduction to Pandas — Series and DataFrames, loc vs iloc, reading CSV and JSON, inspecting data with head/tail/info, and the full data-cleaning workflow for empty cells, wrong data and duplicates.
stats
Quartiles, IQR & Box Plots
Quartiles and the interquartile range, the 1.5 x IQR outlier rule, the five-number summary, and how to build and read a box plot — with fully worked examples.
ml
Classification Algorithms: Logistic Regression to Boosting
Every major classifier explained — logistic regression, KNN, naive Bayes, decision trees, random forests, SVM and gradient boosting — how each draws its decision boundary, when to use it, and the code.
aisearch
The Travelling Salesman Problem: When Search Explodes
Visit every city once, return home, minimise distance. Why brute force dies at 20 cities, how branch-and-bound and the MST heuristic help, and the approximation algorithms that actually ship.
agents
Modern RAG: Beyond Naive Retrieval
The techniques that separate a demo RAG pipeline from a production one — hybrid search, reranking, query transforms, contextual retrieval, GraphRAG, and agentic RAG.
agents
Fast RAG: How Production Systems Cut Response Latency
The latest techniques behind fast RAG responses — streaming and TTFT, ANN indexes, quantized embeddings, semantic and prompt caching, parallel retrieval, and speculative decoding.
math
Bellman–Ford Algorithm
The shortest-path algorithm that handles negative edge weights — and detects negative cycles.
agents
The Agentic Loop (ReAct & Tool Use)
The reason–act–observe cycle that turns a text-predicting model into an agent that gets things done.
diy
Automate a Boring Chore
Make the robots do your repetitive busywork — saving attachments, sending reminders, syncing forms — by connecting apps in Zapier or Make. No code, big payoff.
psych
Emotions & Stress: The Operating System Underneath
What emotions actually are, how the stress response works, why the Yerkes–Dodson curve matters for performance, and the regulation strategies with real evidence — reappraisal, not suppression.
python
Exploratory Data Analysis (EDA) & Plotting in Python
What EDA is and why it comes before modelling — plotting with Pandas and Matplotlib (line, scatter, histogram), and the three levels of analysis: univariate, bivariate and multivariate.
stats
Applying Statistics: Anomaly Detection, Feature Selection & ML
Which measure to use when, outliers as anomaly detection vs noise, using standard deviation for feature selection, and where statistics sits in an AI/ML workflow.
ml
Evaluating Models: Metrics for Regression & Classification
MAE, MSE, RMSE and R² for regression; the confusion matrix, precision, recall, F1 and ROC-AUC for classification — what each number means, when accuracy lies, and how to diagnose overfitting.
aisearch
4-Queens and 8-Queens: Backtracking and Constraint Search
Place N queens on an N×N board so none attack each other. The full 4-queens backtracking trace, why the naive space is 16 million and the smart one is 40,320, plus hill climbing and min-conflicts.
agents
Multi-Agent Systems & Orchestration
When one agent isn't enough — how orchestrators, specialized subagents, and handoffs divide work among many agents.
psych
Fixed vs Growth Mindset: What Actually Changes Minds
Carol Dweck's mindset research explained clearly — what fixed and growth mindsets really are, how they play out in daily situations, what the evidence honestly shows, and how to actually shift yours.
math
Logical Reasoning: Every Problem Type, With Worked Examples
A complete tour of logical reasoning problems — syllogisms, series, analogies, coding-decoding, blood relations, directions, seating arrangements, knights & knaves, grid puzzles, and conditional logic — each solved step by step.
stats
Statistics Reference: Formula Sheet, Traps & Key Takeaways
The complete formula sheet, every number used in class, the exam traps, student questions answered, and the ten things worth memorising.
aisearch
The Water Jug Problem: Production Rules and the Smallest State Space
Two unmarked jugs, no measuring marks, and a target volume. The six production rules, the complete 20-state graph drawn out, the number-theory result that says when it's solvable, and BFS code.
agents
Context Engineering
The discipline of curating exactly what goes into an LLM's limited context window — the successor to prompt engineering.
math
The Doppler Effect: Why the Siren Changes Pitch
The shift in wave frequency from relative motion — the intuition, the formulas for sound and light (with signs that actually make sense), worked examples, and where it shows up from radar guns to redshift.
aisearch
The Monkey and Banana Problem: Means-Ends Analysis
A monkey, a box, and a banana hanging out of reach. The four-part state tuple, the operators, why this problem became the standard test for logical planning, and a full solver in Python and Prolog.
agents
OmniParser: Turning Screenshots into Structured UI for Agents
Microsoft's OmniParser is the "eyes" of a GUI agent — a vision pipeline that converts a raw screenshot into a labelled map of clickable elements. Here's how it works and why it's fundamentally not an LLM.
aisearch
Vacuum Cleaner World: Agents, Percepts and Rationality
The smallest AI problem there is — eight states, three actions. Used to define what an agent is, what makes one rational, and what happens when it can't see the whole world.
aisearch
Issues in Search Techniques: How Search Fails
Combinatorial explosion, cycles and redundant paths, local maxima, plateaux and ridges, inadmissible and inconsistent heuristics, and the four classic design questions — with a diagnostic table for telling which failure you are actually looking at.