Quick answer
OFFICIAL (Steam achievement data, 2026-10-20): the game's star totals are anchored to three achievements:
- Rising Star — Collect 14 Stars.
- Shining Bright — Collect 28 Stars.
- Star Collector — Collect All Stars, and Steam's tracker caps it at 28.
Because "Collect All Stars" and the 28-star milestone carry the same cap, 28 is the verified all-stars ceiling that achievement progress is measured against.
How stars are spread across levels
UNVERIFIED: whether all 28 come from level replays, from grade-only levels, or from mixed bonus tasks is not published level-by-level. The per-level star values shown on result screens remain the ground truth in game.
Note for completionists: maxing every tool is a separate career ladder — see Master of the Trade and the Upgrades reference.