Arena 90 and the Ghost Ladder

Practice gets better when progress is visible. A flat list can be useful, but it does not give a learner much sense of where they are, what came before, or what kind of challenge is waiting next.

Arena 90 is our answer to that problem: a 90-node campaign path over real AlgoArena problems, paired with medals, unlocks, and ghost races so the work feels like a world instead of a spreadsheet.

What shipped

The campaign path is pinned to existing problem IDs. A campaign node should not drift every time the library changes order, and a learner should not open node 42 tomorrow to find a completely different concept by accident.

The current audit is intentionally concrete:

• 90 campaign nodes
• 9 worlds
• deep test coverage across the path
• no node below 100 test cases
• medals based on best test-case progress

The research note on the audit lists the 14 topic buckets the nodes cover and explains why arrays and strings get more nodes than graphs and trees.

The medal model gives partial credit by design. Passing one case earns one medal. Passing at least half earns two. Passing every case earns three. That makes progress visible even when the learner has not fully solved the node yet.

The dashboard also has a card that reopens the campaign in one click.

Why ghosts belong here

Ghosts make empty lobbies feel less empty without pretending offline runs are live opponents. A player can race their own prior accepted attempt or race an eligible human ghost when the run meets the replay bar.

Self ghosts can be useful with looser rules because they only affect the person who created them. Human-pool ghosts need stricter eligibility: accepted and complete, clean practice or battle context, timed replay, enough events and snapshots, and no Rena, AI, hints, or imported context flags. The ghost eligibility note walks through each of those gates.

With ghosts in place, you can practice alone, race a real historical attempt, or jump into live ranked when a match is available.

Why the route matters

The first Arena 90 map had the right idea but the wrong feel. Nodes were readable, but they sat on top of the map instead of belonging to it.

The product lesson is larger than a single art pass. Arena 90 needs the route, curriculum, unlock model, and illustration work to agree. The public contract starts with pinned nodes, coverage, prerequisites, medals, and replay eligibility. The map layer should be drawn around that contract and never used to disguise it.

That is the difference between "a UI over art" and "a campaign whose structure is visible."

What stays separate

Arena 90 attempts are clean-slate practice. Rena, AI, and hints stay disabled for the campaign route. That keeps medal progress and ghost eligibility understandable.

The goal is a clearer signal, so that when a learner earns medals on a node, the product knows what that work represents.

Arena 90 is still a beginning, but it now has a pinned path, visible progress, replayable targets, and a map that is starting to act like a world.