Prettifying it pt.1 (v0.6)

I've finally got to start working on the game's art, yay! I'm pretty happy with the results so far, with a minor problem or another here and there. I planned to release ALL of the art at once, but since I had to tend to other businesses for a couple of weeks last month, I decided to leave the enemies' art for the next update to get this one out sooner. So for the next update, I'm getting more art done and as many fixes and QoL changes as I can. So, onto the list!

Changelist:

• Added new art to the in-game background, in-game UI, powers, and powers' projectiles - animations included;
• Added on-hit feedback to the Stonewall;
• Nerfed the Stonewall. Cooldown: 10 -> 15. HP: 10 -> 8. Stonewall was easily spammable, and most of the time you could summon a new one before the previous one was destroyed;
• Nerfed the Shielder. Pierce resistance: 80% -> 50%. Arrows are too weak, so I'm looking into making the enemies more vulnerable to them.
• Fixed the Fireball not exploding when hitting the Stonewall;
• Fixed the Fireball glitching out when switching powers before it hits a target;
• I've managed to get some help and finished a new enemy spawn system. It is fully functional, but it has little use until the game has actual levels. At least that's a huge step toward getting the first couple of levels done. Until then, I'll keep the current unlimited spawner in use, which might turn into a survival-like infinite mode later on.