Genetos

"Hello, Hello. This is the Planet Genetos. Who are you?"

Genetos is a freeware shoot'em up game with an "evolution" theme. Each level mimics a different era, going from a Space Invaders homage through the nineties and up to Bullet Hell, and each has an associated ship, from a simple left-and-right-moving white blob to a sophisticated weapon of mass destruction with bombs and lasers. The game can be downloaded here.

This game contains examples of:

 * Best Level Ever: Stage 5. 5. Get it?
 * Boss Rush: Can be done in Free Play, by choosing to skip the actual levels and go directely to the bosses.
 * Boss Subtitles: "The Mutant".
 * Which links into the "evolution" theme.
 * Bullet Hell: Starts at the fourth stage. Unless you're playing in Creator mode.
 * Crash Into Hello: Quite literal: Genetos smashes itself into Earth and then calmly introduces itself, hoping to become friends.
 * Crowning Music of Awesome
 * Curb Stomp Battle: When your ship evolves in the middle of a boss fight, the rest of the encounter is like this. Some evolutions encourage you to avoid this, however.
 * Though bosses also start using new attack patterns when you evolve, meaning it is sometimes easier to fight them before evolving.
 * Cute'Em Up: The very first level. The rest of the game is more standard shooter fare.
 * Defeat Means Friendship: Sort of. If you get the Summon Subweapon, you'll be able to summon bosses you already defeated to help you.
 * Evolutionary Levels
 * Evolving Weapon: Your playing style determines what sort of guns you get in later stages.
 * Flying Saucer: The first boss.
 * Gainax Ending: After you get all the evolution energy in the final boss, ...What?!
 * Well, as the text that reads in the Final Generation plainly states,
 * Genius Loci: Genetos itself.
 * Hitbox Dissonance: Averted in the first stages of evolution, where your hitbox is noticeably larger. As you evolve, however, this trope begins to play itself out at face value.
 * Homage: To Space Invaders, Radiant Silvergun, Ikaruga, Rez, and the shoot'em up genre as a whole.
 * Each stage seems to be one, to a different series. Stage one is an homage to Space Invaders, stage two is an homage to mid-80's arcade shooters like Galaga and Xevious, stage three is one to early-90's games like Toaplan games and the Raiden series, stage four is one to Do Don Pachi and the Ray Series, and stage five is one to Ikaruga and Radiant Silvergun.
 * Idiosyncratic Difficulty Levels: Beginner, Standard User, Programmer, Hacker, and Creator.
 * Infinity+1 Sword: Two highly damaging ones can be acquired. While they are tricky to aim initially (they open and close as you move) and start small they do very high damage and virtually fill the screen when used by higher level ships.
 * Interface Screw: The motion blur feature. Even its lowest setting will make your eyes hurt after extended exposure.
 * Laser Sword: Obtained if you play aggressively and get close to foes.
 * Level Up: Your ship isn't necessarily matched to your stage, instead improving when you collect enough of the green pellets dropped by enemies.
 * Marathon Level: The final stage is as long as the rest of the game.
 * One Bullet At a Time: Two bullets with the first ship, five with the second, unlimited thereafter.
 * Puzzle Boss: Stage 5, Part 4.  However, after 100 seconds the game just skips to the next phase anyways.
 * Recurring Boss: The first four bosses are described as "The Mutant".
 * Scenery Porn: Stages 4 and 5.
 * Self-Imposed Challenge: In Free Play mode, you can do things like trying to play the later stages with a Level 1 ship.
 * Certain evolutions will prompt you to defeat that generation's boss with that generation's ship. In some situations, this is easier said than done.
 * To elaborate, not only must you use a weaker ship to beat the boss, you must avoid collecting too many EXP power-ups during the boss itself, and all the bosses are Mook Makers. You could try to avoid the EXP in the stage and time it out, but that's a challenge in and of itself (especially with higher-leveled ships, which tend to attract EXP).
 * Smart Bomb: Five kinds of them.
 * Trippy Finale Syndrome: Which is then further enhanced by using the F5 key.
 * What Do You Mean Its Not Symbolic: The final stage.