Object: create the desired weight.

You are given a scale with two trays and tokens for weighing.
Of each given weight you can have as many tokens as you like.

The combined weights on the left tray minus the combined weights on the right tray have to be exactly the same as the given target shown at the centre bottom.
The weights on the left tray are counted as positive, the weights on the right tray as negative.
If the right tray is heavier than the left tray, the result is negative and the number turns red.

You can copy the top weight of a tray simply by clicking above it.
This way you can easily create a stack of similar tokens without moving them one by one from the supply stack.

To remove any piece from a tray simply move it below the tray and it will disappear.
All weights positioned above it will then drop down one step.

You can also move any piece from one tray to the other.

You win if the 'result' number is equal to the 'target' number.

If you create an extreme unbalance (namely a resulting weight of less than -100), you will lose (the game will stop with an 'error' message).
Any number greater than 600 will also cause a loss.

Beginners level: find a solution.
Expert level: use as few tokens as possible.

Solutions are attached.
All solutions have been found by hand; hence you might be able to improve on them.

Freeplay Variants:
There are also two 'free play' variants included which has all weights available.
In the first freeplay variant you can still set a target.
The second freeplay variant is designed so that children can learn adding and subtracting. No target is set here, and the sums below the trays are omitted as well.

Background design based on an image taken from the 'Clickart' collection by Broderbund.