Flood Fill Screensaver
The Flood Fill screensaver runs a real live flood-fill algorithm, spreading color outward through a randomly walled grid to fill every reachable cell of a region. It is free, runs in your browser, and ESC exits.
How the Flood Fill / Region Growing screensaver works
The saver generates a real random grid of walls and open cells, then starts a flood fill from a random open seed cell.
Each step, the real algorithm visits every unfilled neighbor of the current filled region and adds it to a growing queue.
The fill spreads outward exactly the way a real paint bucket tool works, stopping cleanly at walls and region boundaries.
Once the whole reachable region is filled, it holds briefly, then a fresh random grid and seed cell begin.
A worked example
A narrow one-cell-wide corridor still fills completely, cell by cell, while a wall just one cell over stays untouched — exactly the real reachable-region boundary the algorithm respects.
Settings & tips
- Accent recolours the spreading fill.
- The grid layout and seed cell are real and randomized every run.
- A fresh grid generates automatically once the region fully fills.
Frequently asked questions
- Is this the real algorithm behind paint bucket tools?
- Yes — a real breadth-first flood-fill implementation, the same core technique used in image-editing fill tools.
- Why does it stop where it does?
- It only fills cells reachable from the seed without crossing a wall — a real, exact boundary, not a visual approximation.
- Is a key needed?
- No — it is a pure local computation.
- Is it free?
- Yes — free, no download, in your browser.