let neighbors = List.map (fun (ox, oy) -> ox + ix, oy + iy) offsets in
let neighbors = List.filter (is_onside width height) neighbors in
let neighbor_states = List.map (fun (x, y) -> forest.(y).(x)) neighbors in
let neighbors = List.map (fun (ox, oy) -> ox + ix, oy + iy) offsets in
let neighbors = List.filter (is_onside width height) neighbors in
let neighbor_states = List.map (fun (x, y) -> forest.(y).(x)) neighbors in