How to play
- Goal
- Draw one closed loop that visits every room once, passes through every moon or every sun in that room, and alternates moon and sun rooms.
- How it ends
- A chart finishes when one unbranched loop obeys every room and symbol rule; links remain editable before completion, so there is no loss state.
- Record
- Your first unaided solve time is recorded for each chart; replay is Practice.
- Tap a cell and an orthogonal neighbour to toggle their connecting link. Draw one closed loop with no crossings, branches or revisited cells.
- In each room, visit every moon or every sun, and avoid every symbol of the other kind. Ordinary cells are optional; both turns and straights are allowed.
- Visit every room once. The route enters and leaves each room once; after leaving a room, do not return. A one-cell visit is allowed when it has one entering and one exiting link.
- Alternate moon and sun rooms along the route, including the closing transition. Use Undo or tap the same pair again to repair a link. Restart keeps your original first-solve clock.
Controls
| Mouse / touch | Tap two neighbouring cells to toggle their connecting link |
|---|---|
| Arrows / Space or Enter | Move the cursor / select or complete a neighbouring pair |
| Delete / Escape | Clear selection / clear or return |
| Z / Y / R | Undo / Redo / Restart confirmation |
| Controller | D-pad moves; A selects; X clears; Y undoes; shoulders undo/redo; B clears then returns; Start opens settings. |
Tips for Moon-or-Sun
- Start at corners A corner symbol that would force a visit to the opposite kind in its own room rules out that choice.
- Follow a chosen kind Once a room chooses moons or suns, all its symbols of that kind must be visited and every opposite symbol avoided.
- Count room entrances Each room has exactly two route links crossing its boundary: one entry and one exit.
- Keep one cycle Avoid branches and separate closed rings. Every visited cell needs exactly two links.
Questions about this game
Must every cell be used?
No. Ordinary cells may remain unused. Every symbol of a room’s chosen kind must be used.
Can the two kinds be mixed in one room?
No. Visit all its moons or all its suns, never both kinds.
Can a room be visited again?
No. After leaving it, the route cannot return.
Can a symbol turn or go straight?
Yes. Moon and sun symbols have the same route-shape freedom as ordinary cells.
Does the closing connection alternate too?
Yes. The last and first rooms along the loop must choose opposite kinds.
Can Replay replace my first time?
No. Replay is Practice and retains your first result.
This edition follows Nikoli’s Moon-or-Sun rules. All charts and examples were made for this edition; no published boards were copied. Reload keeps links and Undo; resumed first solves stay local.
Watch how to play
About Moon-or-Sun
Draw one route through every outlined room. Choose moons or suns in each room, visit every symbol of that kind, and alternate the choices around the loop.
All 96 original charts are open: twelve 4×4, twenty-four 5×5 and sixty 6×6. Each has exactly one independently verified loop.
