Qonnect Four

Qonnect Four gets a quantum overhaul! In this reinvention of the beloved classroom classic you still aim to connect four identical pieces, but now you can bend the rules of reality with quantum entanglement.

Instead of placing just one piece, you may entangle two candidate positions. Until the pair is measured, both squares display a shimmering quantum link that belongs to neither player. When a measurement occurs, a quantum circuit collapses the pair into either two circles or two crosses with equal probability.

This mechanic forces you to think several moves ahead, weigh risk versus reward, and even weaponize uncertainty against your opponent. Can you master probability and planning to line up four before your rival?

Quantum Entanglement

Entanglement is a phenomenon where two or more qubits share a single quantum state. Measuring one instantly defines the state of the other, no matter how far apart they are.

In the game, an entangled pair is visualised as two animated placeholders that alternate between a circle and a cross. Without hovering, each symbol grows from the centre and fades before repeating; when you hover over either square they merge into an eye-shaped ellipse that gently pulses outward. These spots still have no fixed owner until they are measured—clicking either one runs a tiny quantum program that collapses the pair:

stateDiagram-v2
    accTitle: "Quantum Entanglement Collapse"
    accDescr: "State diagram showing that an entangled pair stays in superposition until a measurement collapses it to either outcome 00 or outcome 11 with equal probability."
    [*] --> Entangled: Entanglement created
    note right of Entangled: No measurement - pair remains in superposition
    Entangled --> CollapsedX: Measure → X
    Entangled --> CollapsedO: Measure → O
    CollapsedX --> [*]
    CollapsedO --> [*]

Behind the scenes the code uses the quantum-circuit library to create a one-qubit circuit, apply a Hadamard gate, and measure, delivering a perfectly fair 50 / 50 result.

From Physics to Gameplay

1. Create entanglement - tick the Entangled checkbox and place a second piece.
2. Maintain superposition - while the pair is unmeasured it blocks both squares for classical moves.
3. Collapse the state - click either piece to trigger measurement and reveal two identical symbols.