also, yeah, i forgot to mention i believe the over-world shops would be like x8 times the cost. and i don't think you should be able to steal from it, so try to code that the shoppy can't kill you, and you can't steal the items :3
I was thinking more like a menu-shop. It doesn't have the really good items, only bombs, ropes & parachutes (or something), and is very expensive, but when you're underground, you don't have to pay tax (thus cheaper prices) and you can buy illegal stuff like jetpacks
on that note, you should be able to store all items you get back in the map in some fort or something and you will be able to access this at any point when on the map.
Well, yeah, that could be nice. My idea was that you gain items (gloves, shoes, whatever) in gameplay, and that item stays with you on whichever level you play next, whether you replay an old level, or shortcut to another world, or whatever you do. You lose your items and revert back to 4-4-4 Spelunker when you die.
I just had an idea regarding how to "unlock" new worlds: let's say the world map is a patch of desert, and on this patch is a highly expensive market, which sells bombs, ropes, rocks and other cheap stuff (and on rare occasions, slightly more useful stuff). There is also a tent marked "High Scores", inside which a Spelunker lives, and a very old, decommissioned elevator shaft, with a rope/vine dangling to the bottom. The shaft goes very deep, and appears to have four levels, each with an entrance to the Colossal Cave. Only the uppermost door is unlocked - the second, third and fourth are locked from the inside. So you go into Area 1, and there's a series of underground caves, which you traverse in world map style. Screw it, I'll make a diagram.
So you reach the end of Area 1, from which you can progress to Area 2. If you have a Key with you (or a special key, or if you pay the Tunnelman enough, or do some other thing) you can unlock the door to Area 2, saving a lot of time.
Oh and if you die, you have to restart the LEVEL, while if you game over, you restart the WORLD. Or the whole game. I don't know. And to go back, you have to play through certain levels again (maybe just the randomly-generated ones?)
So yeah. That's how I imagine an overworld map would work in Spelunky.