A really well done and interesting mechanic, most of the time though I generally ended up ignoring the WASD movement and played it like a shoot to move game.  Which was definitely a bit more fun in my opinion.  The puzzle use of the coins mechanic is pretty varied though, it's definitely interesting and leaves a lot of openings for future additions.  A bit of finer feedback tho:

• The WASD movement felt really fast and imprecise so I generally avoided using it, instead defaulting to only using the gun.  Which was, relatively fun as I mentioned above.
• Though to get into the gun a bit more, it was a bit imprecise as well, which I know comes with the territory, but maybe with some tweaks, possibly putting it on some sort of "hold longer = bigger blast" kinda thing, it could have some more control for the player and vary up the movement a bit.
• The "dropping coins" mechanic wasn't really... explained.  I sorta stumbled upon it in what I assume was it's intro level but I still didn't fully understand it until the first level "key coins" were introduced, which also weren't too clearly displayed.
• Specifically the "key coins" didn't really have any indication on how many you were supposed to grab to open the doors.  Though it wasn't utilized too much since it showed up late so it was generally somewhat obvious.  But for example the first level with them seemed as though I could do it with only 4, but I ended up needing 5.  Adding some sort of on screen counter could help?  Or... possibly having each one correspond to one block on the screen.  That way you could make it more strategic as to how many to grab, or possibly with different colors which ones to grab.  To allow you to get the least coins while also making an exit.  
• The difficulty curve for the first little bit was relatively simple, pretty well designed and laid out, unfortunately it had a pretty big spike that wasn't really slowed down around when the "key coins" were introduced.  I feel like a couple more introductory levels to them would have helped slightly in making them a little easier to figure out.

That's about all, overall though a pretty fun game to play.  I'd definitely be interested to see where you could take it and see what additions might come up.

It's interesting to play, but the player moves a bit to fast, so it hard to control

And when you collect some coins it just stops shooting and collecting anything till it falls to ground. I thought it would be like: you get more coins you are heavier