Read the track
Scan downward from the launcher and identify the rows and lanes containing stars and black holes.
A mobile-first physics path puzzle with 120 verified levels, a daily challenge, anonymous URL sharing, and a practical strategy guide.
Predict deflectors, straight paths, and portals to avoid black holes and collect every star across 120 verified progressive levels.
Level 92 / 120
Add one tool for each track row, then release the marble.
Add one tool for each track row, then release the marble.
YouToStem · Strategy
Scan downward from the launcher and identify the rows and lanes containing stars and black holes.
Start from the final star: decide whether the previous row needs a straight, left, or right instruction.
Run a partial program, follow the highlighted route, and change only the first instruction where the path diverges.
A mirror portal swaps lanes 1 and 5, swaps lanes 2 and 4, and leaves the center lane unchanged.
Add a deflector, straight path, or portal command for each track row, then release the marble. Avoid black holes and collect every star. Tap a command in the program to remove and rearrange it.
There are 120 deterministic levels across Starter, Junior, Challenge, and Master stages. Tracks grow longer, stars and hazards increase, and advanced stages introduce mirror portals.
Yes. The engine creates a legal hidden route first and places hazards away from that route. Automated tests also replay the hidden program and verify all 120 levels.
Yes. The date creates a stable daily level and track seed, so everyone gets the same puzzle that day. It changes the next day and requires no account.
After winning, choose “Invite Challenge.” The standard header share dialog opens with a link containing the level, track seed, command count, and completion time.
No. Validated challenge data is encoded directly in the URL, so both players can play anonymously without a stored server record.
Players predict how each instruction changes the marble position and debug failed routes, practicing sequencing, state changes, spatial reasoning, debugging, and cause-and-effect thinking.