NOTE: No license - copyright withheld until changed (feel free to clone etc, just don't release or allow generic public access) - I am in favour of an OS license on the client code at the least...

Basic game design ideas.

Introduction

The display uses DHTML (hence browser based) and heavy Ajax use to interact with the server.
All dungeons are instanced so only you and your party are together, however towns are "open" to all.
Display is isometric with a one-button interface.
Server uses PHP + MySQL.
Dungeons are created once and stored for later instancing.
Mobs and items are generated at instance time, only generic types and levels are generated at creation.

User Interface

Browser based - using HTML5 Canvas elements for maps
Isometric tiles
One click to move / attack / collect / etc (no overloading right click)
Clicking on an item with multiple actions gives a menu (dropdown?) of options
Inventory, Equipment, Stats etc are all floating displays in the browser window (only one tab needed).
Keyboard control needed - tab between displays with optional keyboard movement controls at all times
Map (dungeon etc) has LOS (line of sight) - no map data sent to client till they have potential LOS on it
Hidden monsters have an id and fog but don't move when not seen - so player knows last location, but not current location
Map is always reset to "not known" when entering a level - you must explore to fill it
Inventory is grouped and then alphabetical - possibly tabs of types (lazy loading until needed)

Gameplay

While in "public" areas like town there is no fighting or mobs
Game continues running while player is connected - tick of 1 second
Monsters may have different speeds for movement
Pause button (?)
Inventory size limited by weight, possibly with a limited number of items to prevent stupidity :-P
Items can be combined with "natural" results - fire + oil = bad...
Items need identifying the first time - magical items always need to be identified
Item types (such as potions, scrolls etc) only need to be identified once per player - but the "identified" flag follows the item itself

Stats & Experience

Stats are 1-100, internal work is run off square root, so skill power advancement is non linear, but stat gain per level is always the same
Experience per level is linear (exp gain needed to level = 1000 x level)
(Possible) Stats: str, dex, int, wis, con, cha
Players must visit the town to level up (regardless of exp gained)

All these are rough, subject to change, and subject to equipment:

Hitpoints = 10 + level x sqrt(con)
Mana = 10 + level x sqrt(wis)
Party size = sqrt(cha)
Skill points per level = sqrt(int)
Damage = sqrt(str)
Defense = sqrt(dex)

Classes & Skills

Classes only specify starting skills and equipment
Skills are capable of being improved by training (and practice?)
Some skills inhibit others - might and magic don't play nicely
Skills go from 0-100, untrained cannot use it at all
Skill use goes on the square root (affected by sqrt of relevant stat)
(Possible) Skills: might / magic, stealth / armour, accuracy / rage
Cost (difficulty?) of increasing any skill is based on the sum of it and it's opposite

Parties

Players may group together and dungeon crawl as a party
Parties get tougher monsters, but better loot
Player may close window (tab etc) at any time - when the last member of a party quits the dungeon will pause (if player is alone then it will pause when they quit)
One player leads a party
Party size is limited by charisma of leader
Players may "hire" npc's to fill out their party

Server

PHP + MySQL
Client is completely untrusted - all data is checked
Dungeon maps are generated the first time they are visited - they are populated as an instance when someone goes in
Only one instance per player per time - leave a party and lose that instance
Instance is stored until another is created (delete after xx days unused?)
Monsters are capable of having an inventory - only items which affect the monsters stats are created before death (or theft etc)
Inactive data (unused for more than a week?) is automatically archived - restore is transparent and automatic

Maps

Maps are stored in square blocks with a level and coordinates - only terrain is stored in this map data
All map contents including doors are generated when the map is instanced
Not all dungeons go down to the same depth - deepest level is related to the level of the player who first created the last floor of it
(Over time) add more dungeon generation algorithms to give a variety of styles

Instancing

All instance data is stored in an sql table
Map is loaded from database
Random point is chosen to be entrance
"Walk" map (distance from entrance) is created
Random point at 3/4 max walk distance is chosen to be exit (if allowed)
Doors are added in relevant places - depends on rooms entrance etc
Chests are added in random locations
Mobs are added
Any keys added (in mob or chest) must be in a "walk" distance less than the lock (door or chest)

Rycochet/mmo-rogue