The siren sounds a "danger" tone continuously while it is active and
damaged, such that meltdown is imminent. It sounds a one-off "clear"
tone if it has been sounding "danger" and the danger has passed, either
because the structure is repaired or because the reactor has become idle.
The new tool will say whether a target block type is present in a
specified region, to allow for more targeted digging. It is deliberately
quite weak, with several limitations: only stores enough charge for a
small number of shots; target can only be set by pointing at an example
node; range is limited; accuracy is less than 100%. Some of these
limitations should probably be ameliorated, but not entirely eliminated,
in the future when we have a better idea of game balance.
The inventory image is only a placeholder.
