To answer your questions:
1- Can a novice game designer create a survivors like in just one week? Yes
2- Can a survivors like game work with only black and white colors?
Yes
I played to level 50, solid difficulty curve, upgrades, mini bosses. You got it all in here. The only thing I could suggest is to increase upgrade variety. Otherwise, great game!
P.S. Snowflake girl OP haha