The Challenge Cube is the day's second daily puzzle and a genuinely different problem from the Daily Double. The grid is 8×8 per face with 8 colours and a Par of 43 moves — the same budget as the Daily Double's first cube. What changes is the board: roughly one cell in seven is a blocker, a dead cell that never takes a colour and never joins your flood. On a 384-cell cube that is about 57 holes.
Same budget, worse board. That is the whole design: you are asked to solve a fragmented cube on a move count calibrated for a clean one.
Blockers are not sprinkled at random and hoped for. The generator picks candidate cells one at a time, removes one, and then runs a breadth-first search across the whole cube to check that every remaining coloured cell is still reachable from every other. If a removal would cut the cube into disconnected pieces, it is reverted and another candidate is tried. Blocker placement stops when the target count is reached.
The consequence matters when you are staring at an awkward board: the cube is always connected, so a path to every cell exists. What blockers cost you is efficiency, not possibility. There is no such thing as a Challenge Cube whose remaining cells cannot be reached — only ones that take more moves than you have.
Everyone gets one attempt per day, guests included. If you want another go you can unlock an extra attempt by watching an optional ad. The important detail: the cube is generated from a fixed daily seed, so every attempt that day is the identical puzzle. A retry is a second try at the same board, not a fresh roll — which means the first attempt is worth treating as information gathering if you intend to retry, and worth treating as final if you don't.
Your in-progress board is saved as you go, so refreshing or closing the tab does not burn the attempt.
A run of blockers can separate two large same-coloured areas that would otherwise have merged in one move. Before committing, check whether the colour you are about to take is actually connected to your region or merely nearby: on a Challenge Cube "nearby" is often on the far side of a wall and worth nothing this turn.
Blockers make same-face travel expensive, which raises the relative value of edges. A capture that carries your region across an edge onto a fresh face usually opens more options than a bigger capture that stays boxed inside one face. Rotate more often than you would on a clean cube.
A handful of cells ringed by blockers with a single coloured entrance is a pocket. It will cost you a dedicated move eventually, and the move is cheapest when your region is already adjacent to the entrance. Note them early, collect them in passing, and never leave two pockets on opposite faces for the last three moves.
A blocker in the middle of a face removes four adjacencies. A blocker on an edge removes fewer, but it can sever a cross-face link that a whole route depended on. When you plan a path, look at where it crosses edges and check those specific cells.
It is a harder puzzle than either Daily Double cube and a shorter commitment than Power Mode. If you want the blocker problem without the one-attempt pressure, Power Mode's stages also carry blockers at the same 15% rate, and Infinite Zen gives you clean cubes for open-ended practice. The Challenge Cube keeps its own streak, counted the same way as the Daily Double's: days on which you won.
Play today's Challenge Cube, or read the Strategy Guide for the move-selection heuristics these tactics build on.