Maze Solver Robot Simulator for Flood-Fill Planning

Controls

Choose Open course, Switchbacks, or Dead ends, then run the robot at three speeds or advance exactly one cell with Step. Start, Pause, Reset, keyboard shortcuts, and Full screen keep the experiment controllable. The map distinguishes physical walls, mapped walls, unknown edges, known-open edges, visited cells, flood distances, the robot trail, and its current heading.

Theory

A grid maze can be represented as cells connected by passable edges. The robot does not begin with the full graph; it discovers left, front, and right walls from its current heading and records each observation on both sides of the shared edge. Boundary walls are known from the fixed maze dimensions.

Flood fill assigns the center goals a value of zero and propagates increasing values through every edge not known to be blocked. Unknown edges remain optimistically open. When sensing reveals a new wall, the simulator recomputes the field and chooses a safe neighbor one level closer to the goal, preferring unvisited cells and deterministic turns on ties.

Algorithm

1. Align the robot with a cell and classify its left, front, and right edges.
2. Store each blocked or open observation reciprocally for the current cell and its neighbor.
3. Recalculate flood-fill distances when a newly discovered wall changes the known map.
4. Choose a safe neighbor one distance level lower, preferring an unvisited cell, then the smaller turn.
5. Move exactly one cell, record the trail and heading, and repeat until a center goal is reached.
6. Compare the completed move count with the truth-map optimum to measure exploration efficiency.

Source code

Keep the planning core independent of motor and sensor drivers:

void planOneCell(Maze& map, Robot& robot) {
  map.observe(robot.cell(), robot.senseLeftFrontRight());
  map.floodFill(centerGoals);
  Cell next = map.bestDescendingNeighbor(robot.cell());
  robot.turnAndMoveTo(next);
}

Keep sensing, mapping, planning, and motion as separate functions. That boundary makes the same planner testable in this browser lab, on a desktop, and on the final controller.

Circuit diagram

Use an external regulator sized for the motor stall current. The ESP32 and sensors need a stable logic rail even when motors reverse.