“Invalid angle” means the launch arc cannot reach the target from where you stand. Since 1.0 the catapult shows a range indicator while placing, and it refuses targets that are too high or too low for the arc. Fix it by moving the catapult closer, changing the floor gap, or switching to an inclined conveyor for the same route.
The three causes
| Cause | What you see | Fix |
|---|---|---|
| Target out of arc | Indicator does not reach the shelf | Move the catapult one to two tiles closer |
| Height gap wrong | Arc clears the shelf or hits the floor | Catapult up/down one floor, or move the shelf |
| Obstruction in the path | Angle snaps to invalid over a roof edge | Open a gap, or route through a Tunnel Conveyor |
Fix order that actually works
- Prove the feed on one floor. Place the catapult and the target shelf on the same level. If the angle is still invalid, the problem is distance, not height.
- Add height one step at a time. Each floor you separate them narrows the valid angle window; if the indicator disappears, you have overshot.
- Check the ceiling. A block above the launch point kills the arc even when the indicator reaches. Remove the block or move the launcher out from under it.
- Give up on the arc if the route is vertical. A Conveyor Lifter (vertical) or Inclined Conveyor Belt (diagonal) moves the same items without an angle at all — see vertical transport.
What changed in 1.0 and 1.1
- 1.0: range indicators were added to throwing devices, and catapults/cannons stopped selecting targets that are too high or too low. That rule is why a previously working throw now reads as invalid.
- 1.1.5023: no change to throwing devices; the update added the Cargo Lift (16 packages per trip, vertical) which is often the better answer for multi-floor feeding.
What is not documented
There is no published numeric angle window — any guide quoting “45 degrees” is guessing. The game validates the arc against the target position, so the only reliable method is the indicator plus the three checks above.
Still stuck? The unlock path itself is on how to unlock the catapult, and the station comparison is on catapult vs cannon.
Range indicator and target-height rule: OFFICIAL 1.0 patch notes. Cargo Lift: OFFICIAL 1.1.5023 notes. The fix order is OBSERVED play, and no numeric angle is claimed because none is published.
Independent fan reference for Alchemy Factory. Game data refers to the current official 1.0 build (Steam, PC). Field-level evidence is flagged on each page with OFFICIAL / OBSERVED / COMMUNITY badges; amounts shown without a badge come from the official 1.0 patch notes or store descriptions.