Slime Kingdom: Idle

Slime Kingdom: Idle asks you to grow a fortune by sending slime adventurers on quests, hiring others to gather resources, crafting potions and gear, and eventually trading, warring or signing treaties with neighbouring kingdoms. It's a solo developer's first release, priced modestly at NZ$7.89, and the early reception is genuinely split — not on whether the idea has promise, but on whether the execution holds up once the opening hours are over.

An idle game that isn't quite idle

The single most damaging complaint in the review corpus targets the genre's foundational promise. "A decent idle game, but it does not have any offline progression, so can not recommend it," reads one review. A second, much higher-playtime review agrees in four words: "Crashes a lot. No offline progression." For a game explicitly sold as idle, a report that progress doesn't continue while the game is closed — the entire point of the genre for most of its audience — is about as foundational a flaw as a review can raise, and it's notable that it comes up independently from two separate players rather than a single outlier account.

A promising opening, a grinding second half

The fullest review available, from a curator dedicated to idle and incremental games, is worth reading for its balance: "Good first game for a solo dev. First few hours are pretty enjoyable: new gameplay elements are regularly introduced. But the pacing sadly becomes slower and slower the more you progress afterwards." The same review praises the layered systems (quests, units, equipment, crafting, upgrades), calls the UI clean and the art and music solid without being remarkable, and specifically credits the developer as "a real gentleman" who actively tried to help resolve issues raised with him — a good sign for a solo project's future, even where the current build falls short. But it also documents the collapse in detail: "passed a certain point, it takes way too much money to unlock the next quest, to the point it becomes a boring grind," and the late-game "world" diplomacy system — trading, treaties, war with neighbouring lands — is "quite obscure," leaving players "in the dark about what you need to do" to unlock new content, with win conditions left unclear by design or oversight. A separate, harsher review agrees on substance if not tone: "the balance is complete mess... there's no real point to unlocking new quest areas — you get most income if you upgrade earlier ones," and describes upgrading basic slimes into advanced tiers as an outright chore requiring repeated screen-scrolling.

Rough edges

Beyond pacing and progression, there are reported stability issues. One review describes a completely unresponsive first launch — "the game just does nothing, no buttons work" — that persisted through repeated restarts and reinstalls before eventually working. Steam's own achievement data adds one more data point worth knowing: an achievement for playing 999 hours sits at roughly 2% completion, an extreme, almost novelty-tier grind wall that will only ever be meaningful to the genre's most dedicated players.

Final verdict

There's a decent idle kingdom-builder somewhere inside Slime Kingdom: Idle — varied early systems, a distinctive premise, and by most accounts a developer who's actually listening to feedback. But a reported absence of offline progression strikes directly at what makes an idle game worth playing in the first place, and a late-game pace multiple reviewers independently describe as grinding and opaque compounds the problem. At NZ$7.89 the financial risk is small, but there's enough here to suggest waiting for the offline-progression gap to be addressed, at minimum, before buying in.