First playtest feedback

Thanks to Spart4ck, I made the first playtest and here are some changes I made :

- The entrance are now more sensitive, you can go back from the room you were before more easily

-  The shield can now be deployed 0.1s after death, that save you from that death. This technique  will  (I hope)  limit the sentences like "but I  pushed the button that's not fair..."

-  In the "snail room" you cannot avoid the lasers by shielding right in time

- Some bug fixes