Yes, Totally Safe Moon Project is fully playable in single player, and it is a supported mode rather than a leftover: Single-player is listed as a feature next to Multi-player, Co-op and Online Co-op. Nothing in the core loop needs a second player — the height ladder, the "NEXT GOAL" banner, the garage upgrade terminal, the tool grid and the laser delivery all work the same way on your own.
Totally Safe Moon Project single player: what stays the same
Everything that drives the run:
- The first hour. The routine is the same either way, and the beginner tips guide walks through it.
- The height ladder. Every goal on the meter pays out on its own, and the achievements behind them — the height goals, picking up an NPC, the UFO, the trampoline, the boombox — are all solo-friendly.
- The garage. The upgrade terminal, the "Select your Tools" grid and the invite board are all there when you play alone.
- The ending. Hauling the laser up your own tower and firing it at the asteroid is a one-person job.
What you lose without a partner
Two things, and both are about labour rather than rules:
- Carrying. Every prop in the tower has to be lifted by you, so the height meter moves at the speed of one pair of hands — the tower building guide has the carry loop that makes that as fast as possible.
- Cover. A saucer or a meteor shower hits just as often in solo, but there is nobody to keep the stack going while you deal with it, and nobody to help you put the missing third of the tower back.
If you want a second pair of hands
A session holds five players — you plus four friends — and you can invite them from the garage board or with the I key shortcut. The co-op guide has both routes.