I suggest implement:
1. in Android version Synthesia Touchscreen 18 keys (based on Synthesia Virtuial Piano in Windows Version)
2. in Android/WIndows version/versions Synthesia Touchscreen Stylophone (based on Stylophone S-1 https://mixingaband.com/stylophone-letters-to-numbers/)
I my opinion this are good ideas, especialy implement 2. will boost popularity of Synthesia .
The 18 key zoom level should be available in the Android app already. If you tap the magnifying glass icon at the top-right corner, do you see an "18 Keys" choice there?
Otherwise, regarding the Stylophone layout, outside of being numbered, it doesn't appear very different than a standard piano. Or did you mean Synthesia should try to emulate the aesthetic parts like the 45-degree angles on the corners of the (not-)black keys?
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