Level design inspiration and rules?

So I'm creating this open world (semi castlevania world map) 2D-platformer and have some pretty default player abilities I'm happy with, but I'm having problem with setting the rules for how to build the actual game world. Here's what I got:

The whole world is built by connecting screensized rooms in a gridlike fashion. This is done so its easier to build the world and creating a world map.
So far I'm spreading each player ability and enemyclass evenly across the game resulting in that the player have access to them all about 3/4 into the game. With the final quarter focusing on epic player skills.

I've build the character controller so that there's three types of jumps. Easy, medium and hard. Each with different jump length and height.

Each ability and enemy is introduced with Nintendos Mario-4-step mechanic, with increasing difficulty level that also works like a tutorial to making the player need to use and understand the ability.

Today, the outline of the whole game cave- system is doodle-blocked so that no "room" takes to long to get to from any part of the world map. The layout with shortcuts are iterated and pretty finalized.

My problem is that, all the necessary gameplay features and overall rules on how to build the actual game is there, but what about rules to follow for the small parts? The fillers. How do I build (not code) and place the gameplay content (not graphics) for my rooms? Anyone got an idea or resource how to build my levels?

So far I'm thinking about doodling platform structures, and build different ability/hinder combinations (prefabs/kitbash) and see in what order they fit in the game world. <-- This is probably something I need to do since much of this is unique to each game, but maybe someone have this amazing resource for going on about this?

Thanks!

 

I didn't actually get what you mean, but from what I got, your problem is how and where you will place the gameplay events?

In this case, like you said in the Mario step method, progressively add difficulty. Start with 1 enemy there, then add more, change combinations, surprise the player. Most open world games are first introduced in level-like gameplay, placing boundaries in the open world. After the player is tought how to play, he is then unleashed to roam in the world.

 

This is a great question for the Game Design section!

I've linked to this article before, but I think it's very appropriate here: David Kuelz's Narrative Design Tips I Wish I'd Known. The gist is that the game world and gameplay are major parts of the game's story.

Sure, dialogue boxes like "Thank you, Mario, but our princess is in another castle" move the story along. But the player spends much more time experiencing the world (and thus its story) just by running around in it.

Can you order your "rooms" so they suggest a story to the player? Then you can fill each room with the props that support that story.

Here's another good article along the same lines: 4-Layers, A Narrative Design Approach

Another great resource for level design is Scott Rogers' Level Up!