I tried to change the "options" information while calling "Windy API" as below, but it doesn't work properly.

var options = {
key: key, // REPLACE WITH YOUR KEY !!!
lat: 36.4703327,
lon: 128.0149211,
zoom: 8,
map: 'thunderforest:spinal-map',
overlay: 'thunderstorms'
};

var options = {
key: '7A0ASvBKxfCwbMwbDWOFPneRSAzn489P', // REPLACE WITH YOUR KEY !!!
lat: 36.4703327,
lon: 128.0149211,
zoom: 12,
crs: L.CRS.EPSG3857
overlays: ['rain', 'wind', 'thunderstorms', 'temperature'],
baselayers: ['rain']
//map: 'thunderforest:spinal-map',
//overlay: 'thunderstorms'
//overlay: 'ecmwf' /
//map: 'thunder'
};

I hope you understand the direction of how I want to develop "Windy API" and get a positive answer. Have a happy day today!

1. Unfortunately, this map background is not part of our API, so if you want to have anything similar, you need to insert your own map from different provider.
2. No, it isn't, there is no possibility, in general, to change the default map.

1. Currently, if you are above level 11 on the Windy homepage, it will be changed to another map, but is it impossible to make it like this?

2. Is there a way to use 'Rain, Thunder' as the default map?

1. Do you specifically mean our app by that regular internet network, or your version of API?
2. Unforutnately, since the last zoom level, which offers our map with data, is 11, there is no higher zoom possibility in our API.
3. If you mean radar data, there is no possibility to use this layer in Windy Map API.