Kero Blaster is just such a good-feeling game. It's mostly no-shading pixel art. No implying 3D, even at the level NES games did. All flat, almost like Atari, but the iconography is just so delightful. And the second state of those two-state sprites hits the spot. The shocked look of guys when they've been hit is adorbs. The look on the main guy's face when he gets an item: also delightful! And the music is so calmly happy.
Anyway, worth playing to feel good!