Marble Sort Level 307 Walkthrough Solution | Marble Sort 307

Marble Sort Level 307 Guide: The Lock, Key, and Mystery Box Trap

Marble Sort Level 307 is a massive traffic jam waiting to happen. You load in and immediately see a huge, blocky Top Tray stacked high with bright colors. A heavy grey chain with a golden padlock sits dead top-center, locking away the highest light green, dark blue, and yellow marbles. The golden key needed to break that chain is buried on the far left edge.

Down below, the bottom Boxes are stacked in four tight columns. You can see what you need right now, but the columns are loaded with grey blocks featuring question marks. Those are Mystery Boxes. You have no idea what color they will demand until the front box is cleared. If you start pulling random marbles from the Top Tray without a plan, your Conveyor Belt will fill up instantly. One wrong tap in the midgame and you fail.

The Front-to-Back Reveal Pattern in Marble Sort Level 307

Take a hard look at how this board is built before you touch anything. The lowest exposed row of the Top Tray gives you a straight line of accessible colors: light pink on the far left, then pink/red, orange, another pink/red, and dark green on the far right.

Directly above that bottom row is your second layer of bait. You will see more light pink, pink/red, purple, dark red, and blue. Do not pull these early.

The middle of the board is an absolute minefield. A row of Iced Boxes sits horizontally across the center, freezing orange, light blue, white, teal, and purple marbles. Right below those frozen blocks, you have Arrow Box mechanics in play. A light green block is tied to a dark green one. A yellow block is tied to a dark red one. These dependencies dictate your midgame route.

Now look at your bottom Boxes.

• Column 1 (Left): Starts with Orange, followed by two Light Pink Boxes, then a Pink/Red.
• Column 2 (Mid-Left): Starts with Dark Green, hides a Mystery Box, then Light Pink, then Green.
• Column 3 (Mid-Right): Starts with Pink/Red, then another Pink/Red, Light Blue, and Dark Blue.
• Column 4 (Right): Starts with Pink/Red, hides two Mystery Boxes, then Orange.

The jam risk is entirely on the right side of your Conveyor Belt. You need to clear the opening orange and dark green first, but those two right-side pink/red Boxes are the real gatekeepers holding back the Mystery Box reveals.

Marble Sort Level 307 Step-by-Step Walkthrough

Follow this exact order to keep your Conveyor Belt clean and force the board to open on your terms.

Surviving the Opening Clear in Marble Sort Level 307

The first five moves dictate if you survive the midgame. You must clear the immediate front lines to reveal the hidden demands below.

1. Tap the orange marbles in the bottom middle of the Top Tray. Send them down to instantly clear the top Orange Box in Column 1.
2. Tap the dark green marbles on the bottom right of the Top Tray. This clears the top Dark Green Box in Column 2. Clearing this immediately exposes your first Mystery Box.
3. Target the pink/red marbles. You have two blocks of pink/red in the bottom row of the Top Tray. Drop them both. They will drop into the Pink/Red Boxes sitting at the top of Column 3 and Column 4.
4. Stop and look at the new board state. Column 4 just revealed a Mystery Box. You now have hidden demands in both Column 2 and Column 4. Do not pull anything else from the Top Tray until you identify what those grey boxes need.

Digging for the Lock and Key in Marble Sort Level 307

With the bottom row of the Top Tray gone, you have to push down the left flank. Your primary goal is that golden key.

5. Focus on the left side. You exposed a row with light pink and another pink/red. Column 1 has stacked Light Pink Boxes waiting. Tap the left-side light pink marbles to clear the next Box in Column 1.
6. Look at the Mystery Boxes that just opened. If they demand pink/red, use the remaining pink/red blocks you just uncovered. If they demand light blue or dark blue, you are in luck.
7. Start mining the far-left edge. You need to clear the light blue and dark blue blocks sitting right next to the golden key icon. Drop them onto the Conveyor Belt only if you have the matching bottom Boxes exposed.
8. Once the path is clear, hit the block holding the golden key. This triggers the Lock and Key mechanic. The heavy chain at the top center of the board shatters, releasing the top row of light green, dark blue, and yellow marbles.

Breaking the Iced Box Trap in Marble Sort Level 307

The late game shifts the pressure. Your Conveyor Belt will start to feel very cramped as the Mystery Boxes force you to hold onto colors you cannot use yet.

9. Now that the top is unlocked, check your Arrow Box dependencies. Play the light green and yellow blocks carefully. Make sure the boxes they point to are dropped down before you commit them to the belt.
10. Attack the Iced Boxes in the middle row. You need two nearby boxes dropped to activate them. Work your way inward from the cleared left side, dropping the frozen orange and light blue blocks into your active bottom Boxes.
11. Keep the Conveyor Belt moving. If a Mystery Box reveals a brown or purple requirement, use the upper right corner of the Top Tray to fill it. Never drop more than two unmatchable blocks onto the belt at this stage, or the final column will jam you up. Clear the remaining pink and blue stacks sequentially to finish the board.