Uurnog is described by its creator as a "whimsical collect 'em up platformer", and it uses pick-up mechanics similar to Lyle in Cube Sector and Super Mario Bros. 2. In it, you need to get one of every creature on the planet and put them in the save room — the only room that doesn't reset if you die.
The games contain examples of:
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- Ambiguous Gender: Since there is no dialogue referring to any of the characters and nothing is gender-specific, the only way to tell a character's gender is by their hair, and some don't seem to lean either way.
- Bottomless Pits: Any area below the room's lower camera boundary is considered this.
- Color-Coded Stones: A blue gem is equivalent to 1 coin, a green is 3, a gray is 7, and a black is 19. The hidden rainbow gems are 99. Their color and shading are the only things different about their appearance.
- Cool Gate: The teleporter pads. Stand on one, or place something on one, and it goes to the save room.
- Death Ray: The blue gun zaps 1 HP off whatever it hits (enough to kill all animals), but does not effect anything non-organic like boxes or books.
- Developers' Foresight:
- If you go into a shop and warp any of the items there into the save room, they will still have their price tags on them, so you'll have to buy them either way. This also applies if you try putting shop items in a box.
- NPCs in shops have their own coin amounts. This can be observed if you push them around to get them out of their passive mode — they will only pick up free items or items they can afford.
- Most time bombs prompt you to "activate" 0-second time bombs, with no number on them, prompt you to "detonate."
- Disintegrator Ray: The purple gun destroys nearly anything it hits without leaving a trace.
- Double Jump: Played with. If you're holding an item, and you drop it in mid-air, you get a boost the same height as your regular jump. Once you have the inventory, you can drop even more items to get up to a sextuple jump!
- Excuse Plot: Get all the animals together in the save room's animal collector. You're not even told why until the end- they're being featured in a zoo! Uurnlimited lampshaded this in its old Steam description:Enter the wacky & whimsical world of Uurnog Uurnlimited, where you have only one goal: find your way around the world, and steal all the animals! Why? Because theyre adorable, and because video games.
- Forced Tutorial: The game starts with a small set of puzzles demonstrating basic mechanics and controls. Subverted in that there is a secret exit to the left of where you start that isn't too hard to reach once you know where it is.
- Hearts Are Health: The health-restoring item looks exactly the same as the heart that represents your HP.
- Hub Level: The save room.
- Interchangeable Antimatter Keys: Downplayed. Keys are generally assigned to a specific type of door, and will disappear once you use them. However, there is a master key hidden to the left of the tutorial, and in a few secret levels in Uurnlimited which plays this trope entirely straight.
- No Antagonist: As with Knytt. There are a few robot bosses in Uurnlimited, but there's no real reason that you're fighting them other than to get keys and money bags from defeating them.
- Noob Cave: You start in one of these, where you learn the basic mechanics of the game.
- Pressure Plates: Which turn off Frickin' Laser Beams.
- Purely Aesthetic Gender: Then again, every character is purely aesthetic. Even if you hack the savedata to give yourself a character you can't normally select, all characters have the exact same abilities.
- Ray Gun: Comes in six varieties, but half of them can't kill anything and are mostly used for puzzles.
- Secret Shop: Way above the camera boundary in two of the zones are these shops. They sell items for dramatically less than you'd find in the village, but the items are all hidden in plants, so you don't know what you're buying until you pluck it out. Uurnlimited features a third shop after the train level is completed.
- Skeleton Key: The master key. Like every other key, however, it disappears after one use.
- So Near, Yet So Far: The save room is the place you return to when you die, and it's the main passage between other zones, but it's also the spot where you must deposit every animal to get the primary ending. And it's one locked door away from another ending.
- Signpost Tutorial: In the very first room you spawn in, the text explaining the controls and all is projected onto the terrain.
- The Spiny: Most animals have a variant covered in spikes. These behave the exact same, and will count as the same animal if you're persistent enough to get them into the save room's animal collector.
- Teleport Gun: The gray gun sends anything it hits to your "queue", and they'll spawn into the save room once you enter it.
- Time Bombs: Present. Once you turn one on, you can only turn it off with an Uurnlimited-exclusive health gun (although no puzzles require this).
- Wraparound Background: Any area featuring moving clouds in the background will have this.
- You Gotta Have Blue Hair: There are some characters with normal hair colors, but most characters sport unnatural coloration.
- Dummied Out: With developer mode, you can access some "prototype" puzzles which are completely untextured aside from the objects and the foreground.
- Boss Arena Idiocy: The flying bots you defeat to get the Z and U keys would be unkillable if there weren't bombs and guns conveniently laying around. They also mainly "attack" by warping items from your queue into the room, even though the rooms that come before you fight them have bombs and guns that you must enter into your queue to continue.
- Coop Multiplayer: Of the "tag-along" variety. The other player may take control over a dog who is eternally leashed to the first player.
- Debug Room: Containing every book in the game, several creatures, and a floating robot sphere. It can be accessed through a door in the save room that only appears while you're in developer mode.
- Locomotive Level: Which leads to yet another ending.
- Train Job: Cowboys and robot cowboys will frequently pop out of doors in the train levels, holding a gun or a bomb.
- Secret Level: A few, actually, and they can be accessed using any shiny orb with the prompt "???". Your rewards for beating them range from powerful guns to one-use keys that work on any locked door.