Stealth rock now works like spikes, where you need to stack 3 layers of them in order to deal maximum damage, the damage calculation now would work as follows:

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Type effectiveness 0.25x

1 layer------>0.78125%
2 layers----->1.5625%
3 layers----->3.125%
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Type effectiveness 0.5x

1 layer------>1.5625%
2 layers----->3.125%
3 layers----->6.25%
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Type effectiveness 1x

1 layer------>3.125%
2 layers----->6.25%
3 layers----->12.5%
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Type effectiveness 2x

1 layer------>6.25%
2 layers----->12.5%
3 layers----->25%
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Type effectiveness 4x

1 layer------>12.5%
2 layers----->25%
3 layers----->50%