Okay, here is a shot of the battle scene, all the art is purely placeholder:
It may be hard to tell exactly what is going on here. There are 5 colored cubes, one for each party member (red=fighter, blue=healer, yellow=mage, green=archer), and the enemy(grey), each with a corresponding round token along the bottom area.
When the battle begins, the colored tokens begin appearing at the left side of the 4-lane section at the bottom. They are always moving to the right, and disappear off the field when they hit the right side. For each grey token that makes it off the field this way, the enemy gets an immediate attack. Having multiple vertical tokens make it off the field in a single column acts like a critical attack.
The player has the ability to remove the grey tokens from the field before they hit the right side. The player clicks and drags on an adjacent series of three tokens to create combos. They are removed if it is a valid combo.
One such combo is 3 adjacent tokens, where the middle token is grey and the end tokens are the same color. This combo removes all 3 from play, negating an eventual attack from the enemy.
Making a combo of 3 or 4 tokens of the same color will allow the corresponding party member to attack (based on color), then remove the tokens from the field. A match 4 is more powerful than a match 3 obviously.
The healer is slightly different. Instead of getting an attack when a blue match is made, he gets a free heal for one or more party members.
A combo of 3 or 4 tokens of all different colors will partially 'charge' those party members. After 4 charges a character will get an attack.
More difficult enemies may spawn special attack tokens, which have a specific effect if they make it off the right side of the field. For example, one special attack may speed up the token scrolling, or could destroy all tokens along it's rail.
To make it easier for the player to make combos, the player can right click and drag on two adjacent tokens to switch their positions. Thus the player can try to arrange the tokens to make combos before they hit the right side.
If a party member loses all their HP, tokens of their color will be unable to be used in any combos.
Fight is done when one side loses all their HP.
Umm, does that make sense? There are details here and there that may change when I get back to coding and tuning.