Idle Lumber Inc is a timber-industry idle game: trees are felled, logs travel to the mill, the mill cuts them into planks, and the planks are sold. Each stage can be upgraded, and each upgrade shows up immediately in how fast the line moves.
Like most production-chain idlers, the interesting decision is never 'more money' but 'which link is holding everything else up'.
By clearing the bottleneck. In a production chain, output equals the slowest stage, so upgrading anything else has no effect until that stage is fixed.
Yes — the mill keeps running and you collect when you return.
Yes — tap to play. Nothing to install.