Smile Basic: Programming that’ll put a smile on your face
Unleash your creative powers on the 3DS with SmileBoom’s Smile Basic. Everything you need is included to create applications that utilize the powerful features of your 3DS. Documentation can be found here. The North American sale price is $9.99.
Sprite Editing Tutorial
Source: SmileBASIC Releases on the North American 3DS eShop on 15th October