PathBlocker

A Java playground for experimenting with classic path‑finding algorithms on grid‑based “maze” levels. The project comes with a tiny interactive game/visualiser where you control (or let the algorithm control) a yellow agent that tries to reach a black‑and‑white goal flag while obstacles constantly conspire to block the way.

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✨ Key features

Feature	Description
Two grid modes	Flat Grid – every cell has the same traversal cost. Altitude Grid – pyramidal “hills” give each cell a movement cost proportional to height.
Multiple search algorithms	Flat Grid: Depth‑First Search (DFS) and Breadth‑First Search (BFS). Altitude Grid: A* (with Manhattan or Euclidean heuristic – configurable).
Live visualisation	Watch the open / closed node sets grow cell by cell and see the final path traced back.
Level files	Levels are plain text, so you can design your own mazes with any editor.
Pluggable heuristics & costs	Just implement the Heuristic and CostModel interfaces and drop them in.
Unit‑test friendly	Core logic is algorithm‑only – no UI dependencies. JUnit tests included.
Lightweight	Pure Java 17, no external dependencies; runs on Windows, macOS, Linux.

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📸 Screenshots

Flat grid (BFS)	Altitude grid (A*)

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⏱️ Algorithms in a nutshell

Algorithm	Grid type	Notes
BFS	Flat	Uses a FIFO queue; explores layers outward.
DFS	Flat	Simple stack‑based exploration; mainly for comparison.
A*	Altitude	Priority queue ordered by f(n) = g(n)+h(n).

Heuristic functions for A*

Name	Formula	When to use
Manhattan	`	dx	+	dy	`	4‑way movement, cheap & admissible.

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🚀 Getting started

1. Clone & build

Gradle (recommended)

git clone https://github.com/your‑username/pathblocker.git
cd pathblocker
./gradlew run            # downloads JDK 17 toolchain automatically

Maven

git clone https://github.com/your‑username/pathblocker.git
cd pathblocker
mvn javafx:run

2. Play

1. The start menu lets you pick Flat or Altitude grid.
2. Choose an algorithm: Flat grid ➜ BFS or DFS Altitude grid ➜ A* (pick heuristic)
3. Click Start – the solver will animate its search. • Space pauses/resumes • N advances one step (great for teaching) • R reloads the same level • L opens the level picker

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🛠️ Extending the project

• Add a new algorithm:

  1. Create a package under search/youralgo.
  2. Implement the SearchAlgorithm interface.
  3. Register it in SearchRegistry.

• Custom cost models or heuristics: Implement CostModel or Heuristic, drop the class on the classpath, and select it from the UI.

• Make bigger levels: Level files are simple ASCII art:

  ##########
  #S     ###   S = start
  #   ##   #   G = goal
  #  ^^^   #   # = wall
  #   G    #   ^ = altitude (height increases with count)
  ##########