Prepare for a simple technical explanation.
With Ren'py you have to declare from the first version ALL the possible variables that could be needed in the game.
If you have a clear Idea (aka don't care about what patrons tell you), you go straight writing your limited number of variables, and use them.
If you want to create something expandable (like SummerTimeSaga - perfect example), everytime you add new content and insert a new variable Ren'py crashes and it requires a fresh start to "read" the new variables. heh.
Other monkeys uses random things like: var_1, var_2, etc. until var_9999 but that's not professional and leads the development into chaos.
However, this particular engine (on the contrary of Ren'py), is windows\android\SteamOS\MAC\Linux\browser ready, which means that game is 100% compatible with these platforms
natively.
Of course, we are talking about point-click games, not "straight forward" visual novels like "skip skip skip - fuck - choice - skip skip skip - etc".
Oh, I was forgetting, that with Python(shit), if you make a single writing typos (even like a single more space): EVERYTHING could lead to a crash.