Interactive animations & tools for learning computer science — from electricity and logic gates up to algorithms, data structures and a working CPU. Vanilla HTML & Canvas, no installs.
Electricity pulses from a power source through logic gates, building an 8-bit byte that becomes a colour and a musical note. Flip inputs by hand and watch the value change.
A Von Neumann CPU runs a tiny program. Step through every micro-operation as data flows across colour-coded buses between RAM, the registers (PC, MAR, MDR, CIR, ACC) and the ALU.
Watch bubble, insertion, selection, merge and quick sort rearrange an array bar-by-bar. Live comparison and swap counts, with play, step and speed controls.
Two searches race on the same sorted array. See why linear is O(n) and binary is O(log n) by comparing how many cells each one checks to find (or miss) the target.
Draw walls on a grid and watch BFS, DFS, Dijkstra and A* search for a route. See how A* heads toward the goal and explores far fewer cells than blind search.
Add and subtract numbers bit by bit, watching carries ripple from the LSB. Subtraction shows the two's-complement trick (A + NOT B + 1), plus bitwise AND/OR/XOR and shifts, with carry and overflow flags.
Click bits to build a number and see it in binary, denary, hex and octal simultaneously, with the place-value sum spelled out. Then encode any text into bytes.
Encrypt and decrypt with the Caesar shift (and crack it by brute-forcing all 25 shifts), then see how an XOR key scrambles bytes and unscrambles them when applied twice.
Watch factorial and Fibonacci unfold as a tree of calls and returns, with a live call stack. Toggle memoisation to see Fibonacci stop recomputing the same subproblems.
Push and pop a LIFO stack, enqueue and dequeue a FIFO queue, and build a binary search tree — then animate in-order, pre-order and post-order traversals and value search.
Explore every gate through its truth table, then toggle inputs on a live full-adder circuit and watch signals light up the wires as gates combine to add three binary digits.
Write real assembly, assemble it into numbered mailboxes, and run it instruction by instruction — watching the accumulator, program counter and memory change. The programmable sequel to the FDE cycle.
Load an assembly program and follow the Little Man as he carries values between the registers, the ALU and memory along the buses, one micro-step at a time, with a quiz mode that asks what happens next.
Two's complement mantissa and exponent the OCR way: convert both directions step by step, normalise, add and subtract in binary, and see the range-versus-precision trade-off, with exam-style practice.
Click cells to read their indexes, then trace nested-loop algorithms line by line as the grid lights up. GCSE and A Level modes, OCR Exam Reference Language or Python, memory layout, exam questions and a quiz.
Instantiate bank account objects and call their methods, trace a constructor, test encapsulation, follow method lookup through inheritance and run a polymorphic loop, in OCR pseudocode or Python.
Inspect a page's source, build CSS rules live, and write JavaScript that really runs against a mini page with every DOM call traced. Covers the OCR tag and property lists, client versus server, exam questions and a quiz.