EntCSFree, interactive, no sign-up
Explore. Visualise. Understand.
Algorithms, discrete maths, the theory of computation and the maths behind machine learning, each explained in plain language and paired with a visualiser you control: change the input, play it, rewind it, and watch the pseudocode follow along.
Start here
Three good places to begin.
- Algorithms
Sorting algorithms
Seven sorts on the same input, with comparison, swap and write counts side by side.
Try it: Sorting visualiser with seven algorithms and a comparison table - Tools
Graph traversal visualiser
Draw a graph, then animate BFS, DFS and Dijkstra with the frontier shown.
Try it: Drawable graph with BFS, DFS and Dijkstra animation - ML maths
Attention
Q, K and V for three tokens, a live score heatmap, and the weighted sum of values.
Try it: Three-token attention calculator with a score heatmap
Algorithms
All algorithms pages →Each page pairs a careful written explanation with a visualiser you can drive yourself: change the input, step forwards and backwards, and watch the pseudocode follow along.
- Explainer
Big-O notation
Count the steps in real loops, then compare n, n log n, n² and 2ⁿ on a live chart.
Try it: Growth-curve chart and a step counter for five loop shapes - Explainer
Recursion
Watch frames push and pop on the call stack for factorial and Fibonacci.
Try it: Call-stack stepper for factorial, Fibonacci and memoised Fibonacci - Explainer
BFS vs DFS
A queue against a stack: draw a graph and see which order each search visits it in.
Try it: Graph-traversal visualiser (BFS and DFS on a drawable graph) - Explainer
Sorting algorithms
Seven sorts on the same input, with comparison, swap and write counts side by side.
Try it: Sorting visualiser with seven algorithms and a comparison table - Explainer
Binary search
Halve the range, probe the middle, repeat: with lo, mid and hi drawn on the array.
Try it: Binary-search stepper with classic and lower-bound variants
Discrete maths
All discrete maths pages →The mathematical toolkit behind algorithms and logic. Every topic has worked examples you can check by hand, then an interactive version that computes the same thing.
- Explainer
Sets, relations and functions
Shade any set expression on a Venn diagram and test a relation for its properties.
Try it: Venn-diagram expression shader and relation-property checker - Explainer
Proof by induction
Four worked proofs revealed one step at a time, and a broken one to diagnose.
Try it: Step-reveal proofs and a numerical claim checker - Explainer
Combinatorics
An exact nPr and nCr calculator, and a Pascal’s triangle that shows its own addition rule.
Try it: nPr / nCr calculator with enumeration, and Pascal’s triangle - Explainer
Boolean algebra
The laws, De Morgan, and normal forms, with a truth-table generator built in.
Try it: Truth-table generator with CNF, DNF and equivalence checking
Theory
All theory pages →What can a machine compute, and what does a program mean? Start with finite automata you can build and test, then move on to domain theory.
- Explainer
Finite-state machines
Build a DFA in a table, see it drawn, and run strings through it one symbol at a time.
Try it: DFA builder and step-by-step string tester - Explainer
Domain theory
Why recursion needs least fixed points, and how CPOs, Scott continuity and powerdomains supply them.
Try it: Fixed-point iteration stepper (Kleene chain for factorial)
ML maths
All ml maths pages →Four ideas that most of modern machine learning rests on. Each page shows the formula, works a small example you can check with a calculator, and then lets you change the numbers.
- Explainer
Gradient descent
Drag the starting point, set the learning rate, and watch it converge or blow up.
Try it: Draggable loss curve with learning-rate and step controls - Explainer
Vectors and embeddings
Bend the plane with a 2×2 matrix and measure how close toy word vectors are.
Try it: 2D matrix-transform playground and cosine-similarity explorer - Explainer
Softmax and cross-entropy
Edit the logits and watch the probabilities, the loss and the gradient update live.
Try it: Editable logits with live probabilities, loss and gradient - Explainer
Attention
Q, K and V for three tokens, a live score heatmap, and the weighted sum of values.
Try it: Three-token attention calculator with a score heatmap
Tools
All tools pages →Small, fast tools that run entirely in your browser. Nothing you type is sent anywhere, and there is nothing to sign up for.
- Tool
Truth table generator
Expression in, truth table out: with DNF, CNF, a minimal form and LaTeX.
Try it: Boolean-expression parser and truth-table generator - Tool
Graph traversal visualiser
Draw a graph, then animate BFS, DFS and Dijkstra with the frontier shown.
Try it: Drawable graph with BFS, DFS and Dijkstra animation - Tool
Recursion tree visualiser
Paste a recursive function or a recurrence and see its call tree and call count.
Try it: Call-tree drawer for JavaScript functions and recurrences
LaTeX
All latex pages →A small corner for paper writing: formatting rules that most theory venues share, what changes at the camera-ready stage, and a template we wrote ourselves.
- Guide
Formatting a CS paper in LaTeX
Page limits, \documentclass, front matter, theorem environments and the bibliography.
Try it: Pre-submission checklist you can tick off - Guide
Camera-ready checklist
Fonts embedded, PDF/A, copyright form, source bundle, and why final versions get rejected.
Try it: Camera-ready checklist with progress saved in your browser - Guide
LaTeX templates
Where the official classes live, plus a minimal article template you can copy.
Try it: Template builder: pick options and copy the generated preamble
Why visualisers?
Most of computer science happens in steps too small and too fast to see. Reading that quicksort “partitions around a pivot” is not the same as watching the pivot settle into place while the comparison counter climbs, and then trying the input that makes it slow. Every visualiser on this site computes the whole run in advance, so you can step backwards as easily as forwards, and every one is paired with a written explanation, worked examples you can check by hand, and references to the original sources.
There are 21 pages so far, and everything runs in your browser. Read more about the site.