Purple

Purple is a freeware platformer game by Stanislav Stoyanov ("Rolling Cat").

The game is about a purple Waddling Head who escapes from prison with his Precision Quided Frisbee, only to meet Satan-lookalike thereafter who teleports him to a faraway land. That's pretty much what is there about the plot.

Purple draws, as the author states, inspiration from Super Mario World and the MOTHER series. There are 6 straightforward worlds with occasional Bonus Stages where player can earn 1-Ups and points. Each new level introduces a new gimmick to the game (either an old recolored enemy or an object appearing only once). There's also a dozen of various weapons for the player to find.

This game is also very hard. The author also made a (somewhat self-depreciating) playthrough for anyone who thinks it's too hard.

Purple provides examples of:

 * Acid Pools: In stage 2-5.
 * Adventure Towns: World 3
 * Auto-Scrolling Level: Stages 2-3 and 5-2
 * Background Boss:
 * Band Land: In stages 3-2 and 6-6.
 * Blackout Basement: Several caves are this, especially in night stages.
 * Bonus Stage: One for each world. You can enter them by pulling a hidden trigger in one stage.
 * Boss Corridor
 * Boss Arena Urgency:
 * Bottomless Pits
 * Breather Level: World 6 has much shorter stages than earlier worlds, and then there's Final Destiny.
 * Build Like an Egyptian: In World 4.
 * Cats Are Mean: In World 5, you can meet cat-shaped demons who throw explosive threadballs at you.
 * Cave Behind the Falls: If you find a waterfall, we advise you to enter it like a doorway.
 * Chain Lightning: The Zapper weapon.
 * Charged Attack: For every weapon you get.
 * Check Point
 * Continuing Is Painful: Choosing to continue the stage from the checkpoint will make you unable to earn 100% on that stage unless you start again from scratch.
 * Convection, Schmonvection: At one point you have to jump across platforms that rapidly dip into the lava.
 * Disconnected Side Area: Stage 2-3 has a chamber with a switch to Bonus Stage right above a room with a Check Point. The only way to reach the switch is somewhere in another stage.
 * Down the Drain: Stages 2-2, 4-2 and 5-4.
 * Drop the Hammer: One the most powerful weapons in the game.
 * Eleventh-Hour Superpower
 * Fireballs: You can throw them For Massive Damage.
 * Freeze Ray
 * Giant Space Flea From Nowhere: For a game where most bosses are humanoid,  is rather... unexpected (unless you look into the game files).
 * The Goomba: Slimes
 * Goomba Stomp
 * Green Hill Zone: Stage 1-1
 * Gusty Glade: Seen around in World 5.
 * Harmless Freezing: The only thing Freeze Ray does is freezing enemies for a maximum of 3 seconds, unless it's a boss, in which case the freeze ray can only harm them.
 * Heart Container: You get one for defeating each boss.
 * Hearts Are Health
 * Heli Critter: The aqua-colored slimes.
 * Hell Hotel: Stage 3-3
 * 100% Completion: Doing so may give you an award.
 * Hyperactive Metabolism: Averted. Picking up food gives you only points.
 * Ice Palace: Stage 5-5
 * Inconveniently-Placed Conveyor Belt
 * Interface Screw: Touching a certain object will cause the screen to shake and the left and right buttons to be reversed.
 * Invincibility Power-Up: The moon power-up.
 * Invincible Minor Minion: The barrel and trashcan enemies.
 * Kill Streak: Stomp multiple enemies without touching ground to rack huge points and eventually extra-lives.
 * Lava Pits: In stages 1-4 and 4-4.
 * Leitmotif: If Fresh Juice is playing, expect to see an Auto-Scrolling Level.
 * Load-Bearing Boss: Demonic and Flameye
 * Make My Monster Grow:
 * Man On Fire: Frow World 3 and onwards, you can encounter people with burning heads (and later, freezing ones).
 * The Maze: Stage 4-4
 * Mirror Match:
 * Mirror World:
 * Mutually Exclusive Powerups: Picking up one weapon discard the other.
 * Nintendo Hard: Expect to die a lot already on the first stage.
 * No Name Given: Everyone except for the bosses.
 * Number of the Beast: On the entrance to The Very Definitely Final Dungeon. You can even break it if you wish so.
 * Our Demons Are Different: They are humanoid and possess same weapons player can do.
 * Palmtree Panic: Stage 2-1 (no palmtrees though, just trees)
 * Pipe Maze: Not so much mazes however (there could be mazes, but all alternate routes are blocked off).
 * Precision Guided Frisbee
 * Product Placement: In 3-2, you can see advertisements for Coca-Cola and Earthbound.
 * Puzzle Reset
 * Random Encounters: On the world map, stepping on the blank node may result in a battle with a demon.
 * Recoil Boost: With Plasma Gun.
 * Rewarding Vandalism: Destroying TVs may yield out some goodies.
 * Save Game Limits: The game doesn't save progress you made within the world. It does, however, save the gems and records you got on each. The author admitted that it's horrible.
 * Scoring Points: There's even a highscore screen which stands out a lot from other menus, as a left-over from work-in-progress version.
 * Slippy-Slidey Ice World: World 5
 * Sound Test: With each track unlocked as the player first hears them.
 * Spikes of Doom: In three varieties. Short ones that merely hurt, long ones that kill instantly and retracting ones.
 * Spread Shot: Spread Frisbee
 * Springs Springs Everywhere: There are also green ones that mark the Level Goal.
 * Stalactite Spite: Icicles in World 5.
 * Super Not-Drowning Skills
 * Timed Mission: Almost every level.
 * Underground Level
 * Underground Monkey: Slimes come in four variations. Green (the basic one), orange (jumps), teal (takes off and flies) and yellow (leaves spikes when killed).
 * Underwater Boss Battle: Demonic can rise the water level in order to electrify you.
 * Vaporware: This game has been in development for at least 2 years before being released in August 2009.
 * The Very Definitely Final Dungeon
 * Waddling Head: Most characters in the game, including yours.
 * A Winner Is You
 * Where It All Began: The cell from the intro is where you also.
 * Wrap Around: In vertically scrolling areas.