Games like PixPhys
Games like PixPhys include People Playground, Kerbal Space Program, Space Engineers, Garry's Mod, and BeamNG.drive. We matched them by the tags players give PixPhys on Steam (Sandbox, Physics, Pixel Graphics, Space, and Simulation): closest matches first, and among equally close ones the better-known games.

People Playground
Shared: Sandbox · Physics · Singleplayer

Kerbal Space Program
Shared: Sandbox · Space · Physics

Space Engineers
Shared: Sandbox · Space · Physics

Garry's Mod
Shared: Sandbox · Physics · Moddable

BeamNG.drive
Shared: Physics · Simulation · Sandbox

Kerbal Space Program 2
Shared: Sandbox · Space · Physics

Dyson Sphere Program
Shared: Space · Automation · Simulation

Besiege
Shared: Sandbox · Physics · Simulation

Hardspace: Shipbreaker
Shared: Space · Physics · Simulation

Space Engineers 2
Shared: Sandbox · Space · Physics

Spaceflight Simulator
Shared: Sandbox · Space · Simulation

Noita
Shared: Physics · Pixel Graphics · Sandbox

Stardew Valley
Shared: Pixel Graphics · Sandbox · Simulation

Stormworks: Build and Rescue
Shared: Sandbox · Physics · Building

Terraria
Shared: Sandbox · Pixel Graphics · 2D

Brick Rigs
Shared: Sandbox · Physics · Building

Universe Sandbox
Shared: Sandbox · Simulation · Space

Scrap Mechanic
Shared: Sandbox · Physics · Building

Graveyard Keeper
Shared: Pixel Graphics · Sandbox · Simulation

Totally Accurate Battle Simulator
Shared: Sandbox · Simulation · Physics

Poly Bridge
Shared: Physics · Sandbox · Simulation

Empyrion - Galactic Survival
Shared: Simulation · Space · Sandbox

Cities: Skylines
Shared: Simulation · Sandbox · Building

Teardown
Shared: Physics · Sandbox · Singleplayer