Well, thought I'd get some opinions on Metroidvanias, those platforming games where you explore areas, gaining new abilities that expand the territory you can reach. Metroid and Castlevania are, naturally, the trope namers for providing quality examples of the genre. Sometime I should try out the Castlevania side of that. Anyway, over at GDL, I'm trying to pick up some pace with making an Untitled Platformer that will dip into Metroidvania as well as more traditional sorts along with RPG. So, anyway, I'm asking for examples of stuff you love or hate to see in these games.
Some of my thoughts:
I hate obstacles that only exist so that you can destroy them with a particular weapon. If you need the heat ray to open red doors and the ice beam to open blue ones, that's a sign of lazy design. You can get away with some of that when it makes some physical sense, like drilling into cracked walls, but too much of that can get old. I especially hate it when color swapping an obstacle means you have to upgrade.
A map is a must. I needed a guide for Metroid 1 to get anywhere, and most of my Metroid 2 time was eaten up by wandering back and forth trying to figure out whether or not a particular path was one I had been down, or a new one that was a copy-paste job. When they added the map to Metroid 3, I was ecstatic.
Some obstacles don't have to make sense. In the Metroid Prime series, I liked a number of the morph ball puzzles enough to not care about fridge logic and accept the crazy explanations of the mechanisms for moving spheres about.
Tap into Survival Horror: Early in a new Metroid game, I'm very cautious. When you're still weak, an enemy or trap popping out from behind a corner can be terrifying. Surviving a series of narrow scrapes or finding a safe spot brings satisfying relief, and an urge to brag the first few times you accomplish the feat... Especially if you end up having to do it without all your stuff. Space pirates are much scarier when you're naked.
Sometimes, declare peace. It confuses the hell out of your players: Not every location needs enemies or traps. Sometimes you can drive a "narrative" just by setting a tone with an empty region to navigate. Silence can be scarier. And of course, when you finally do spring something on your players, well, you might want to leave Eversion's start up warning on the game: "Not recommended for children or those with a nervous condition."
Forget block puzzles. Unless it's particularly clever, the game isn't about solving arbitrary puzzles, it's about finding new areas with your expanding list of abilities.
Forget endurance bosses. I don't think Metroidvania bosses should be about simply outlasting the boss. You should have to be clever to reliably avoid his attacks and strike his weak spots. I recommend looking at some bosses from An Untitled Story... Maybe a bit easier. Sometime I need to beat that game. I've made it to the Dark Castle.