The P8 smartwatch is good one to hack and put Espruino onto it. It can be updated without taking apart and is quite cheap ans has full touchscreen and 240x240 ST7789 display.
Here is demo of Espruino build with display driver implemented as Inline C code.
This uses DMA in similar way as the spilcd driver but was written from scratch without using nordic SDK to learn about ST7789 and nrf52 EasyDMA and SPI hardware (first version just bitbanged SPI RXD and TXD registers without using DMA).
BTW it is interesting how much JS interpreter is slower, try to use g.jsflip and see the difference, the code is otherwise the same. While Espruino performance is otherwise OK here it really struggles.
SDK14 and SDK11 based builds are here with some instructions.
Oh and BTW thanks for cube animation, it was stolen from pixl.js conference badge code