A new ZX Spectrum is coming (time to learn Z80 machine code!)

Z80 assembly language tutorial, part 2: text and graphics (ZX Spectrum)

Z80 assembly language tutorial, part 3: user input (ZX Spectrum)

Z80 assembly language tutorial, part 4: movement & collisions (ZX Spectrum)

[SpeccyTuts] Intro — setting up environment, first program

Let's learn Z80 Assembly! Part 1: ZX Spectrum memory layout, video RAM, development environment.

Steins;Gate on the Speccy?! Z80 Assembly Part 2: Stack, Registers, Interrupts, 128K Memory Map