Well done on the art, and I like how you don't even need a tutorial and can just jump straight into the gameplay. Keep it up!
Although, I did crash after round 1:
############################################################################################
ERROR in
action number 1
of Mouse Event for Left Pressed
for object upgrade_card:
Variable <unknown_object>.amount(100030, -2147483648) not set before reading it.
at gml_Object_upgrade_card_Mouse_4
############################################################################################
gml_Object_upgrade_card_Mouse_4 (line -1)