Tracks in the Kiel diagram of 10 M_⊙ (right) and 17 M_⊙ (left) models, with the surface nitrogen compared to the initial surface abundance on the color scale, minding the fact that a lighter color indicates a larger amount of nitrogen on the surface. The top panel shows models with different levels of initial rotational velocity (blue scale), where the models of either set on the left side have an an initial rotational velocity of 15% of the critical rotational velocity; whereas the models on the right have initial rotational velocity 40% of the critical rotational velocity. These models do not include mixing based on IGWs. The bottom panel shows the models with different levels of envelope mixing based on IGWs and do not include the effects of rotational mixing. The tracks that branch off to lower log(g) are those with log(D_env/cm² s⁻¹) = 5 for the 10 M_⊙ model and log(D_env/cm² s⁻¹) = 6 for the 17 M_⊙ model. The other two tracks have log(D_env/cm² s⁻¹) = 0.