Snow blows in through windows

[Ciber Ninja]

Simple. interior tiles adjacent to an open / broken door/window when it's snowing should get snow buildup.

Seems like a relatively easy thing to add.

Next level would be to pre-annotate tiles during map compilation with their distance to the nearest entrance. Which could be use for snow piles that build up over time, but could also be used for more complex effects like puddles during heavy rain or scaling interior erosion over time.