Wheels 
About this appWheels is an Android game specially designed to check how fast your abstract thinking is and how good your math skills are!
60 levels in
total, and every one of them features a different set of
wheels that are connected together and transmit the rotational
motion to each other. You will be challenged to find out various
attributes related to their motion, such as the direction of
rotation, the gear ratios, or the diameter of some wheels. At
first, notice that all these sets of wheels (or gears without
teeth) are considered perfect gear trains, and second, here is a
list of the general rules that are valid throughout the whole
game:


Direction: the objective of this level type is very simple  you have to figure out the direction in which the driven wheel will rotate, clockwise or counterclockwise. Keep in mind that the adjacent gears always rotate in opposite directions. As you know which way the input gear rotates, all you have to do is to imagine how the motion propagates through the gear train and tap the appropriate button to answer. The biggest button, SPIN, will then start the rotational motion, enabling you to verify if the output direction was selected correctly. Ratios: the objective of this level type is to correctly estimate the gear train ratios. As you may already know, a gear ratio is the ratio of the number of rotations of a driver gear to that of a driven gear. For a gear pair, this is equal to the ratio between the diameters of the driven and driver gears. And a gear train is nothing else than a bunch of gear pairs, so simply multiply all these gear ratios to obtain the global value. Tap the button showing this result and then tap SPIN to start the rotational motion and verify if the gear ratio was selected correctly. Spinning: the objective of these levels is to determine if the redcolored wheel can properly spin in the gear train, and, if it does, in which way. As the directions in which the input and output gears rotate are both known, you only have to carefully analyze how the motion is transmitted to the red wheel. Select your desired answer, then tap SPIN to start the rotational motion and see if your choice was correct. Equal Ratio: the objective of these levels is to correctly estimate the diameter of the marked gear, knowing this time that the gear train ratio is 1:1 (equal). This is somehow similar to the Ratio levels, but now the result is given, also the formula and all diameters except for one. Calculate that diameter, tap the appropriate button to answer, and then tap SPIN to start the rotational motion and verify if the result was selected correctly. Estimation: the objective of these levels is to correctly calculate the gear train ratio, the required wheel diameters being known, all except for one wheel. This is somehow similar to the Ratio levels, but now you have to visually estimate the diameter of the marked wheel. Considering this diameter, calculate the ratio and select the appropriate button to answer, then tap SPIN to start the rotational motion and verify if the gear ratio was selected correctly. Rotations: the objective of the this level type is to correctly determine the number of full rotations the driver gear has to make until all the wheels align again in their initial position. This is somehow similar to the Ratios levels, but now you have to take into consideration the ratio of each gear pair. Calculate this minimum number of turns, select its corresponding button and then tap SPIN to start the rotational motion and see if the number was correctly determined.
The game's final
score is displayed when level 60 is complete, and your possible
ranks are as follows:


Global features
 intuitive, easy to use interface
