A battery-operated computer mouse (500, 100) comprising a housing to enclose electrical components of the computer mouse, the housing having a rear palm-rest region (514b, 114) and a front region opposite the rear palm-rest region (514b, 114); and a battery holder disposed within the housing, characterised in that the battery holder comprises a first battery slot sized to hold a first battery of a first battery size, and a second battery slot alongside the first battery slot so as to be in a side-by-side arrangement with the first battery slot, the second battery slot sized to hold a second battery of a second battery size, the second battery size being different from the first battery size, wherein the electrical components of the computer mouse (500, 100) are powered by either the first battery of the first battery size inserted into the first battery slot of the battery holder or the second battery of the second battery size inserted into the second battery slot of the battery holder, wherein the battery holder is disposed in a manner so as to serve as an adjustable weight distribution mechanism to shift a centre of gravity of the computer mouse (500, 100) between a first predetermined centre of gravity associated with the first battery of the first battery size inserted into the first battery slot of the battery holder and a second predetermined centre of gravity associated with the second battery of the second battery size inserted into the second battery slot of the battery holder, wherein the second predetermined centre of gravity is rearward of the first predetermined centre of gravity with respect to the front region of the housing. a housing to enclose electrical components of the computer mouse, the housing having a rear palm-rest region (514b, 114) and a front region opposite the rear palm-rest region (514b, 114); and a battery holder disposed within the housing, characterised in that the battery holder comprises a first battery slot sized to hold a first battery of a first battery size, and a second battery slot alongside the first battery slot so as to be in a side-by-side arrangement with the first battery slot, the second battery slot sized to hold a second battery of a second battery size, the second battery size being different from the first battery size, a first battery slot sized to hold a first battery of a first battery size, and a second battery slot alongside the first battery slot so as to be in a side-by-side arrangement with the first battery slot, the second battery slot sized to hold a second battery of a second battery size, the second battery size being different from the first battery size, wherein the electrical components of the computer mouse (500, 100) are powered by either the first battery of the first battery size inserted into the first battery slot of the battery holder or the second battery of the second battery size inserted into the second battery slot of the battery holder, wherein the battery holder is disposed in a manner so as to serve as an adjustable weight distribution mechanism to shift a centre of gravity of the computer mouse (500, 100) between a first predetermined centre of gravity associated with the first battery of the first battery size inserted into the first battery slot of the battery holder and a second predetermined centre of gravity associated with the second battery of the second battery size inserted into the second battery slot of the battery holder, wherein the second predetermined centre of gravity is rearward of the first predetermined centre of gravity with respect to the front region of the housing.