Cobalt Star Idle is a Chrome side-panel idle game, and version 1.8.5 is the current version as of November 8, 2026. Its Chrome Web Store listing began as Sidebar RPG Idle 0.1.0, so this post is the comparison: what the first version was, what it became, and what I still have not verified.
What version 1 was
Version 1 was a tapper. You tapped enemy waves, four small child stars orbited and attacked on their own, raider ships threatened the core, and combat had elements and a spellbook. Prestige came in two layers, Ascend and Singularity. Spending meant gacha-style cosmetics. It saved locally, had no account and collected nothing.
What it is now
The loop was replaced, not extended. You light and level a procedural galaxy of 3,840 stars. The Calculator levels stars for you, the Attendant plays the same actions you do, and a Supernova collapses the galaxy for Dark Matter and permanent income. A Hypernova is a deeper second reset that pays Cores. There are seven Formulas, three Trials and 44 achievements.
The Underverse and the Keepers
After your first Supernova, a violet counter-force starts swarming lit constellations. Each swarm taxes a little income until it is cleared. Battles are optional: you pick one of four postures (steady, hold, press, ambush), and the forecast you see is a full simulated fight, not a guess. Four Keepers fight beside you: Neutron Warden, Prism Weaver, Comet Skirmisher and Lantern Mender. They rank up to rank 3, learn a trait and carry a racial perk. Battle effects are calm by default, and the whole Underverse can be switched off in Settings.
Spending what you earn
Dark Matter and Cores used to be scores. Now they are also a balance. The Store sells skins, Keeper frames and three small capped Formulas: Resonance (+4% all income a level), Catalyst (+8% Computation a level) and Vault (+1 hour of away time a level). There is no premium currency and nothing is sold for money. Spending never lowers your income multiplier, because the lifetime totals stay put and only a separate spent counter moves. A Hypernova resets the Formula levels and refunds their Dark Matter. There is a quiet Ko-fi link after your first Hypernova; nothing is locked behind it.
What review found
Three things are worth naming because they were not caught by the green test suite. After a battle, cleared swarms did not remove themselves from the list. In simulated fights, Ambush was the best posture in 53% of picks, which makes the other three decorative; per-kind foils brought that to 32%. (Metric: share of best-posture picks across the design-gate simulation. It describes the simulator, not real play.) And buying or equipping in the Store dropped keyboard focus, which a keyboard user would hit on every purchase. All three are fixed in 1.8.5.
What is not verified yet
- Real Chrome rendering and pacing. The screenshots are real captures of the extension, but price and cap balance in long real play is untested.
- Whether the Web Store accepts the Ko-fi link as written.
- The late-game balance of bosses against the Press posture.
Data and sync
The game saves in your browser. There are no accounts, no analytics and no server of mine. If Chrome Sync is on, the optional sync setting also keeps a compressed copy of your save in Chrome’s own sync storage so progress can follow you between browsers. It is on by default and has one switch in Settings. The privacy policy says the same.
The project page is at dhseadev.online/projects/cobalt-star-idle.