What online tool helped you understand music in 12 keys?

As we start piano I feel that the concept of 12 key proficiency doesn’t come for a while because of the sheet music crutch or learning basic songs.

We’re there any tools that helped you understand instant transposition, intervals or was it just practice that elevated your playing beyond just being comfortable in say C major, when for example jamming.

Or are you also on the journey of being more comfortable across the board