The second Goemon game on the N64, and this one's exclusive. It is a 2.5D platformer with co-op gameplay. The game has an overworld map similar to the one found in Super Mario Bros. The difference is that not every point is a new platforming level to jump around in and whack enemies. Some are towns, where you can talk to villagers, buy items or refill health.
At the end of each area (An area is made up of towns and stages - there are 5 areas) there's the boss castle to contend with. You can only enter these castles when you've collected the entry passes from the stages. You enter the castle, fight your way through, and at the end, face the boss. After the boss, the game somehow turns into a first-person segment where you fight mechs. Then it's on to the next area to repeat the cycle.
It's not all mech blasting & platform jumping action. There are significant 2D side-scrolling puzzles, the kind that could be found in a Castlevania game. Then there are different characters to play as (With different abilities and paths through an area) and even vehicles to ride in. You can also revisit stages for fun, or for special tasks that some NPC characters ask you to do.