Teh_Bucket (Electric Charge + Shot sound):
https://creativecommons.org/licenses/by/3.0/

Twemoji (UI Icons)
https://creativecommons.org/licenses/by/4.0/

Kenny (Buildings & Roads)
https://creativecommons.org/share-your-work/public-domain/cc0/

Freesound (other sounds)
https://creativecommons.org/share-your-work/public-domain/cc0/