For now, this project is the first test I did in order to ensure that the cell phone of my friend will connect to the captive portal without trouble. And the test is positive!
The next step (for software) will be to test more complex user interactions and than build the html pages that will support the 6 challenges of the puzzle box.
References :
https://stackoverflow.com/questions/63587623/add-multiple-spiffs-files-to-captive-portal-on-async-web-server-on-esp32
https://github.com/me-no-dev/ESPAsyncWebServer/blob/master/examples/CaptivePortal/CaptivePortal.ino
https://randomnerdtutorials.com/esp8266-web-server-spiffs-nodemcu/
https://circuits4you.com/2018/01/31/upload-image-png-jpeg-to-esp8266-web-page/
https://github.com/125K/ESP8266_WiFi_Captive_Portal_2.0
https://randomnerdtutorials.com/display-images-esp32-esp8266-web-server/
https://github.com/me-no-dev/ESPAsyncWebServer
https://github.com/me-no-dev/ESPAsyncTCP
https://randomnerdtutorials.com/esp32-esp8266-input-data-html-form/
https://randomnerdtutorials.com/esp32-esp8266-web-server-physical-button/
https://github.com/me-no-dev/ESPAsyncWebServer/blob/master/src/ESPAsyncWebServer.h
https://microcontrollerslab.com/esp32-asynchronous-web-server-espasyncwebserver-library/