You see a grey box with a ? on it, and suddenly the whole level feels less friendly. That is the Hidden Box feature in Marble Sort. It does not attack you. It does not move. It does something worse: it hides information.
A Hidden Box covers the color of a box, so you cannot tell which marble color belongs there until you reveal it. This matters because Marble Sort is all about planning your drops before the conveyor gets too crowded. When one or more boxes are hidden, you are forced to play with missing information. Bad guesses fill the conveyor. Good pathing opens the board.
Simple idea. Mean execution.
A Hidden Box is the grey box marked with a ? symbol. It acts like a blocker because it hides the box color underneath. You do not know whether it needs purple, green, yellow, red, blue, or another color until the hidden box is revealed.
The box does not reveal itself randomly. You have to expose it by opening a path beside it.
In plain terms:
That last part is key. A revealed hidden box is not special anymore. It becomes a regular color box that you can fill and clear.
The fastest way to deal with a Hidden Box is to clear the visible boxes touching it. Look at the boxes directly beside, below, or around the hidden one. Those are your open paths.
Use this step order:
Do not waste moves trying to guess what the hidden color might be. The game does not reward blind tapping. It rewards opening the correct path before the conveyor gets packed.
If the Hidden Box is sitting above a visible box, clear the box under it. If it is between two visible boxes, clear whichever side is easier. If it is stuck in a corner, work toward that corner early.
Corners are nasty. Especially the top-left.
The Hidden Box feature is tricky because it blocks your planning. In normal levels, you can look at the board and decide which colors are safe to drop. You know where the purple marbles should go. You know whether green has a home. You know if yellow is worth sending now or saving for later.
Hidden boxes break that comfort.
Here is what they do:
The worst version is when the level hides a needed color deep behind other boxes. You keep waiting for a matching box to show up, but it is already there, covered by a grey ?. That is how hard levels trap you. The color is not missing. It is buried.
Your main goal is not to clear random boxes. Your goal is to reveal information without clogging the conveyor.
Follow this plan:
Clear nearby boxes first Start with boxes that touch a Hidden Box. Revealing hidden colors early gives you more control over the level.
Do not chase easy matches too far away A visible match on the other side of the board can be tempting, but if it does not help reveal anything, it may be a weak move.
Watch the conveyor space If the conveyor is already crowded, stop opening new problems. Clear what is already moving before dropping more marbles.
Reveal one hidden box at a time Opening too many hidden boxes can flood your brain with new colors and new priorities. Reveal one, react, then move.
Target corner hidden boxes early Corner hidden boxes are easy to ignore. That is exactly why they are dangerous. If a hidden box sits in the top-left or another deep corner, start working toward it before the board becomes messy.
This strategy keeps the level stable. You get more information, but you do not turn the conveyor into a traffic jam.
If a Hidden Box is buried in a corner, do not save it for later. Open that corner first or second, even if another match looks easier. The game loves hiding the color you need in the least convenient place, and the top-left corner is a classic trap.
One messy but useful trick: leave one safe marble slot open on the conveyor before revealing a hidden box. That way, if the hidden color appears and you immediately need to shift priorities, you have breathing room. It is not pretty, but it saves runs.
Treat every Hidden Box as missing information, not just a blocker. Your job is to reveal it before the conveyor gets out of control.
Open the nearest path. Check the color. Sort fast.
That is how you beat Hidden Box levels clean.
