Platforms you can jump up through but stand on, and drop down from

Thin platforms are easy to get wrong: the character gets yanked on top while jumping up through them, falls through when standing, or cannot drop down at all. Here is the rule that decides, step by step, whether this platform is solid right now.

Why this works

A platform you can pass through is solid only from the side the player came from. So the rule must look at where the feet were a moment ago, not just where they are, otherwise a rising jump would catch on the floor it is meant to pass.

When not to use it

Skip it when platforms must block from below as well, such as in a game with ceilings the hero hits its head on, or when the player should not be able to drop through. Use ordinary solid ground there and a separate marked kind for drop-through.

In the full entry

• What to build, step by step
• Starting values and the reason for each
• 4 common mistakes and the fix
• A diagram of every state
• 33 lines of example code with 5 checks that pass
• How your AI shows you that it works

Say this to your AI

Use the Spielerando entry "Platforms you can jump up through but stand on, and drop down from" (read_entry one-way-platform-pass-up-land-from-above) in my game. Build it step by step, and show me how you checked that it works.

Or skip this and connect the MCP: your AI then finds all of this by itself.Connect the MCP