This needs the ability to angle the gun and shoot at that angle.
The enemies can shoot at an angle but you can't?
Being an homage to Contra like you say, it should really have it.
Contra also has jumping up through platforms and hold down and jump
to jump down. It's also too easy in terms of enemy AI compared to Contra.
It is very good for 1 day to make and 1 day to polish though, nicely done.
Add what's needed, make some of the backgrounds less dull, improve the AI,
toss in some powerup weapons like spread shot, machine gun, and laser gun,
add boss battles at the end of levels and you've got a nice robot version of Contra!
Good stuff.