#DHSeaDev — Chrome MV3 — Side Panel Extension
Cobalt Star Idle
An idle game about a procedural galaxy of 3,840 stars. Light them, let the Calculator level them, then collapse the galaxy into a Supernova and do it again, stronger. It lives in your Chrome side panel and keeps earning while you are away.
Side Panel
Idle
Procedural
No Accounts
No Network
The Galaxy
3,840 Stars
A procedural galaxy you can pan and zoom. Light a star, level it, and finish constellations for bonuses.
The Calculator
Levels stars for you, choosing the best-value level-ups from a scan window. Pick its target: best value, newest, lowest or a pinned star.
The Attendant
Wakes at your first Supernova and plays the same actions you do, at a pace you choose: Cruise, Steady, Sprint or Overdrive.
Supernova & Hypernova
Collapse the galaxy for Dark Matter and permanent income. Hypernova is a deeper second reset for later.
Formulas & Trials
Seven permanent Formulas, plus three optional Trials with harder rules, daily quests, comets and 14 achievements.
Receipts
A ledger of everything the Calculator, the Attendant and you spent. Share it, copy it, or save it as a PNG or .txt.
Offline Progress
Keeps earning at 60% while the panel is closed: 12 hours, up to 24 with Supernovas.
Open in a Tab
Alt+Shift+O (changeable) opens the game in its own tab, with a wide two-column layout.
What was hard about it
The hard part of an idle game is not the idling, it is the arithmetic that happens while nobody is watching. Cobalt Star accrues resources offline, which means the game has to reconcile “how long was I away” against “what did I already pay you for” every time it wakes.
That reconciliation is where the real defect lived: a storage race that could double-count accrual, crediting the same elapsed window twice when two contexts woke close together. It is invisible in ordinary play and obvious in a headless simulation that fast-forwards days of play in milliseconds, which is how it was found.
The lesson generalised past this game. Any accrual that reads a timestamp, computes a delta, and writes a new timestamp is a read-modify-write, and read-modify-write across two contexts is a race unless you make it one.
Support & credits
Made by DHSeaDev. Free, no ads. If you enjoy it, you can support the developer on Ko-fi. Bug reports: Dhseadev@gmail.com. All projects
Privacy Policy
Your game is saved locally in your browser. Cobalt Star Idle makes no network requests, has no accounts, no analytics, no ads and requests no website access. Nothing leaves your device unless you choose to share or copy a receipt or save.
Read the full privacy policy · Contact: Dhseadev@gmail.com