Really nice pixel art on the zombies, I also liked the way the coins move towards the turret.
There are some flaws on the slow mechanic (you can spam the key and it recharges enough so you can stop time again with every stroke) but nothing that can't be fixed easily by adding cooldown between uses.
The mechanic by itself is a good idea, I'd like to see more upgrades and different enemies, for example ones that throw things at you within a range, so you have to target those first (maybe also hit their projectiles), you know, stuff that makes you think when and what to shoot rather than just shooting everything on the screen! ^^
Overall solid game! Nice work!