A concrete starting point
Scale degrees: 1 2 3 #4 5 6 7
C D E F# G A B C
Compare centers, not just starting notes
C Lydian shares its pitch classes with G major. A shared collection does not make those two centers interchangeable. Play a quiet C pedal, repeat the tonic and end short phrases on C. Then compare the same notes with the parent-major tonic emphasized. A scale diagram lists pitches; it does not establish the harmonic center of a performance.
Try a focused comparison
Play a C major chord and compare F with F#. Then use C–E–F#–G–E–C as a short original pitch sketch, keeping the durations your own.
Write the pattern before speeding up
Use the formula 1 2 3 #4 5 6 7 relative to a C major scale. Keep the seven successive letter names and adjust their accidentals. First play the collection slowly upward and downward, including the upper tonic, then improvise a three-note response with a clear ending. Change one degree at a time when comparing a parallel mode. Correct spelling makes that degree relationship easier to see than a chromatic list of piano keys.
Put it into practice
These examples describe explicit written notes and relationships. A diagram or generated phrase does not replace listening to a complete musical context, choosing a comfortable register or checking a physical technique with a teacher.