Prognose - tricktaking cardgame

Prognose is a trick-taking-cardgame, where each player has to estimate his/her expected number of tricks in each of the five available colors at the beginning of the match. Each too much or too less estimated trick will result in negative points.
The game is a game center turn-based game, that can only be played online. The players don't have to play at the same time, they will get a push-notification if it's their turn.

Short rules
The startplayer plays a card. The following player have to serve this color if it is available. If this color is not available, any other card can be played. The card with the highest value wins the trick, if it serves the first played color. Red is always trump and wins every trick. If the player plays a red card on another color, he/she can decide if the trick will be counted for the first served color or for red color.
The trick-taking-player will be the startplayer of the next round.

Scoring
Each too much estimated trick costs -2 points, each to less estimated trick costs -3 points. The player with the most points wins the match.

Special cards
The creator of the game can choose if king- and ghost-cards should be used. If he/she decides to use those special cards, each player gets one ghostcard and one kingcard. These cards can be played at any time. The king wins every trick but loses against the ghost. The ghost loses every trick but wins against the king.