Super dig this game. Bullet heaven at its core, yes a tad difficult, but a fun challenge. Crucial to survival on my better runs: obtaining and upgrading specifically the Attack Boost and Spread Shot powerups, which means priority targeting the tan-jacketed Agents for their pink Phone drops. Regardless of the other Phone Abilities taken, those two seem most critical.
Also I enjoy the skill involved in scrambling to shoot the weakest enemies, collect powerups and beef myself up before even stronger mobs start appearing. Gotta be quick about it, and avoid Q-Berts with their high HP early on.
Lastly, I appreciate the history and nostalgia of all the great (and crappy) Atari stars and easter eggs of the 2600 era, and enjoy STILL playing "Name That Game Character" with some of the enemies encountered. Would totally love to see other achievements and goals added, such as kill X-amount of Q-Berts, Pac Mans, etc... Great job!