Autumn: This is an excellent upbeat ambient track. I think that the slow introduction of new elements to your song adds to the fact that this will be a literal introduction to your game. I think the driving rhythm adds interest to the listener. I think the collection of sounds you use work very well together and I really like the ambient sounds in addition to the wind-like build-up sounds you use to transition into different sections of your song.
Winter: The collection of sounds here gives a frigid feel which is apt for the winter theme. I also really like the balance you strike with the musical “meat” of the chords and the atonal background bell/clicks and think you have a nice mix.
Overall: I think you do an excellent job setting up your soundscapes. One suggestion I have is that adding some variety in chord progression and making your bass line different from your melody line can add even more interest to your songs and make it so that a 2+ minute loop does not sound repetitive no matter how long you spend in the level. I would be very interested in hearing what your spring and summer themes would sound like!