Evolution of the H-profile slope s = dX/dQ as a function of effective temperature. The evolutionary model grid is built by varying the initial mass, convective overshooting, semiconvective mixing, rotation and initial metallicity (see text for parameter range). The sub-panels are divided based on the input overshooting and initial mass ranges. The tracks are colour-coded based on the input semiconvective efficiency. The black dots mark the end of the MS where central H mass fraction X_c falls below 0.01.