Could anyone explain for a non-gamer what this is? I gather it's a game, it's graphically simple but in fact is really hard, and it was a commercial success ea

Could anyone explain for a non-gamer what this is? I gather it's a game, it's graphically simple but in fact is really hard, and it was a commercial success early on (due to a Humble Bundle?) -- but I haven't really played games since the ZX Spectrum was new. Never heard of it, or the developer, and I have no idea what people are/were excited about. (For other ZX Spectrum era folks: it sounds like a harder "Manic Miner" and I hated that.)