Understand what a computer actually is.

Underneath every game you've played and every message you've sent, a machine is doing something almost absurdly simple: reading a number, deciding what it means, and doing what it says. PlayASM lets you program that machine yourself, one instruction at a time, with nothing hidden and nothing automatic.

PlayASM is a complete CPU simulator and a hands-on programming game. Write real assembly, step through your program and watch every register, flag and byte of memory change as the processor makes each decision. Then take those skills and build something of your own.

Learn by doing: 150+ missions

Start from zero. Missions take you from your very first instruction to real problem solving, each with a short explanation and a hands-on challenge.

• 70 guided tutorial missions covering bits, bytes, hexadecimal, logic, shifts, loops, jumps and the stack
  
• 100+ challenges, from simple exercises to genuinely tough problems
  
• Build reusable subroutines and learn to think like the machine

No prior experience needed. If you already code, the later challenges will still make you think.

See everything. Hide nothing.

• Code Editor with syntax highlighting, autocomplete and breakpoints
  
• Register Bank and Memory View updating live in hex, decimal and binary
  
• Step-by-step execution with adjustable speed, from one instruction at a time to full speed
  
• Statistics panel with performance, instruction, memory and interrupt data
  
• A real, compact instruction set: 16 registers, a 64 KB address space and flags that drive every decision

A whole machine to play with

Once you know the basics, the CPU comes with a full set of simulated hardware, all memory-mapped and all yours to command:

• Three video modes: text, tiles and sprites (scrolling, parallax, collisions) and a raw 320x200 framebuffer in the style of VGA Mode 13h
  
• 8-channel chiptune synthesizer with ADSR envelopes, stereo panning, portamento, PWM and a built-in song sequencer
  
• Robot arm with 6 joints, a gripper, sensors and a conveyor belt
  
• Voxel Sandbox: a 3D world with creation tools, actors, logic circuits, sand and water physics, and growable crops
  
• Keyboard, timers, interrupts, DMA and memory banking, the same ideas real hardware uses

Build whatever you can imagine

Draw fractals pixel by pixel. Compose a soundtrack. Write a text adventure, a platformer or a scrolling shooter. Teach a robot arm to sort objects by color. Wire a lever to a door in a 3D world.

Make it your own with mods

Extend the machine with your own custom devices, with full Steam Workshop support. A mod is just a folder with a JSON layout and a Lua script, with its own window and memory slice. No compiling, no restarting. Share yours and install what others build.

Who is it for?

• Curious players who always wondered how computers really work
  
• Students and self-taught programmers who want to truly understand what's under the code
  
• Fans of programming and puzzle games looking for something with real depth
  
• Retro and chiptune enthusiasts, tinkerers and makers

This is not a toy version of how computers work. It's the real mechanism, built small enough to fully understand.

Available in 12 languages

English, Deutsch, Español, Français, हिन्दी, Italiano, 日本語, 한국어, Português, Русский, Türkçe, 中文