Brain Out Level 138

Overview

A tangled pipe network covers the screen with red valves and one green bowl at the bottom, and the prompt asks to open the fewest switches that will deliver water to the bowl. Most valves lead into dead-end branches, so the solution requires tracing the connected path from the bowl back to the source and opening only the valves on that route.
The pipe network is dense with red valves, and most of them sit on branches that never reach the green bowl at the bottom.

• Difficulty: Hard
• Estimated moves: 4

Step-by-Step Solution

1. Start from the red bowl at the bottom and follow the pipe connected to it upward through the yellow joints. Ignore valves that sit on branches you cannot trace back to the bowl.
2. Trace each branch to see whether it reconnects toward the bowl or ends in a closed loop. Mark only the valves that sit on the continuous route leading to the bowl.
3. Tap those required valves to turn them open. Leave every other switch closed so the number of opened switches stays as small as possible.
4. Press the OK button once the minimum set of valves is open and water can flow along the traced route to the bowl.
5. If water does not reach the bowl, retrace the path to a missed valve rather than opening extra switches; extra open valves violate the least-switch requirement.

Put your starting point at the bowl and follow the connected pipe upward, marking every joint you pass so you do not trace a branch twice. Continue backward until you have identified the full route, then tap only the valves on that route and leave all other switches closed. Press OK once the minimum set is open and water can flow along the traced path. If the bowl stays dry, retrace for a missed valve on the true path; do not open extra switches just to push water through the maze.

Strategy & Reasoning

The level combines pipe routing with an optimization constraint. The least-switch rule means you cannot simply open every valve, so spatial tracing matters more than speed. Following the pipe from the destination bowl backward avoids opening branches that look connected but actually loop away. Opening only the valves on the true path satisfies both conditions: water reaches the bowl, and the count of switches stays minimal. The least-switch rule turns this into a routing optimization: opening every valve would deliver water but violate the constraint, so backward tracing from the destination keeps the open set minimal. The puzzle rewards spatial follow-through over speed, because the dead-end branches look connected at first glance but loop away from the bowl.

Tips & Common Mistakes

• Trace from the bowl backward, not from the source forward, so you do not open unnecessary branches.
• Do not flip every red valve; branches that dead-end should stay closed.
• Confirm the path before pressing OK, because extra open switches break the least-switch condition.