Quick answer
Make the base usable before making it large
Keep a clear access path, place one visible structure at a time, confirm it registered, add available defenses, and test the route back from a short island trip before expanding.
100 Days in the Sky Base Building Guide
The official game confirms base structures and defenses. This guide provides a safe planning sequence while keeping recipes, costs, stats, and placement limits explicitly unverified.
Step-by-step
A safe base-building sequence
Use observable checks instead of assuming unsupported mechanics.
1. Read the available build choices
Use only names and requirements visible in your exact-game session.
2. Protect an access path
Choose clear space and avoid blocking the route you use to gather and return.
3. Test one placement
Confirm the preview accepts the position and the placed structure remains before repeating the pattern.
4. Add available defenses
Cover the most exposed approach using what the current game makes available; do not assume hidden range or damage values.
5. Test a short expedition
Travel only far enough to confirm you can return and use the base as a recovery point.
6. Expand after the test
Add more structures or defenses only when the current layout solves a real survival problem.
What should I build first?
Use the structures the current session exposes to establish a usable base before expanding outward.
What is the best base layout?
No exact-game grid, collision, attack path, or placement-limit evidence is currently source-ready.
Should I add defenses before exploring?
The official description links structures and defenses to survival, so a defensible fallback is safer before longer island trips.
What if a placement does not register?
Retry one piece in clear space using the visible placement preview, then confirm it persisted before adding more.