It's fun I played for some hours, only the hardest mode with Katana.
My complaint which is more of a personal opinion rather than objective criticism is about the power up system.
You get forced to choose between a selection at the start but personally I only like some types of weapon so I ended up killing myself until I got one of the weapons I enjoyed playing. The increasing upgrade cost makes it a major disadvantage to switch to a different weapon after you've picked one.
My suggestions are towards allowing the player more freedom to choose a specific weapon or build. They are one of the following, from simple to ideas that could change how the game is played:
- Let the player look at upgrades, and choose to cancel and not to pick one. This way they can wait out to see if the weapon they want is offered in the next wave at the cost of being weaker for the current wave. (I could not find a way to cancel upgrades, if there's one and I'm stupid let me know)
- Let the player keep the current level/upgrade of the weapon they're using when switching to a new weapon. This way if the player is dealt a "bad hand" at the start they will be forced to play some rounds with a weapon but will have the option to switch later, depending on luck.
- Let the player freely swap their weapon+powerups build with a turret, either during the game or during setup. This way if you get a weapon you don't like you can swap with a turret
Other things I'd like to mention is that I found the repair +/-% a bit confusing. I'm not quite sure whether +repair (as in turret repairs more) is good or -repair is good (as in turret needs less repair)
And I don't understand why, on the first level: I get a free turret+turret upgrade is within budget but player upgrade is out of budget
As far as I can tell you're handicapping yourself by not picking the turret and it takes more skill so I'd allow the player on the first level to choose between a weapon and forgo the turret (or the upgrade) if they feel like going turret-less just for the fun of it.
Edit: Oh I almost forgot. Esc pauses/unpauses the game but it's also the shortcut in the browser to leave fullscreen.
That means that when you pause the game with Esc you exit fullscreen and it becomes impossible to get into fullscreen and unpause the game because the browser will exit fullscreen when you press esc to unpause. So you need to unpause the game and switch to fullcreen with the game unpaused, which can be a problem if you're in the heat of combat.
This can be fixed simply by providing a clickable button to unpause the game or changing the pause key from Esc.