Players like to spend time on games, and they also like to brag about their progress. This is why leaderboards and achievement systems were invented; they help the player to share in-game breakthroughs with some friends and make them public. The leaderboard is a pretty simple system, it displays some score records, operating with player's names and number of received points. A table of achievements in its turn is a more festive thing. It marks all the players' efforts with special rewards: small pictures that play a role of game's milestones. People value any recognition of their efforts so much that each achievement they get in the game makes them happy. The favorite ones are achievements received after a hard gaming scene, for instance, the achievement symbolizing the victory over a big enemy boss or the achievement for special hidden bonuses being collected.
The following screenshot shows different achievements for the Blueprint 3D game, developed by Kostya Stankevych and published by FDG Entertainment:
All the achievements should have a clear and plain description. The players' objective must be easy to catch, something like:
Play the tutorial level
Solve 10 puzzles
Collect 50 stars
Unlock the Advanced mode
Finish the game at the Medium level
There is an unspoken rule of graphic style these achievement icons are using: the illustration needs to be simple, comprising only flat objects, few colors, high contrast, and outlines and should not have soft shadows or any other raster effects. So, they look almost like a newspaper's comic illustration. Of course you can choose a different approach, but try to avoid a big number of tiny details and complex textures.
The achievements usually have very simple plot: a few recognizable elements from the game in a specific combination and a some large text. Because games are part of entertainment, good sense of humor is always welcomed; for instance, the very scary game Ala n Wake from Remedy Entertainment features very funny achievements, for instance, to discover some coffee thermoses and watch TV shows.
There are some clichés among the achievements: today very popular are various trophy cups, laurel wreaths, coins, gold medals, and other symbols of victory. There's nothing wrong with such images other than that they are boring; therefore, always try to push the limits of your imagination.
Each social gaming network has its own specification of images designed for the achievement table. Gamecenter from Apple, for example, utilizes images in special round frames, so the illustrations have to be properly centered to look nice.