-nsp--update 1.0.4-.rar: Snow Bros Special

First, identify the platform. Since it's an NSP file for Switch, the development environment should involve Nintendo's tools, which are not publicly available. But since homebrew games often use Libnx (a library for developing on Switch), maybe the user has access to the source code or the game is a homebrew mod that uses Libnx. Alternatively, if the game is closed-source, the user might need to reverse-engineer it to add features, which can be complex and might have legal implications.