The Debug Menu was used by the Monomi Park developers to easily test the game. It was disabled after Update 0.2.2, although a reddit post gave a tutorial on how to use the menu by modifying C-Sharp.
It was accessed using keybindings as seen here. The numbers refer to the keys above the letters on the keyboard, The numpads do not work, most likely.
|[||Decrement time of day|
|]||Increment time of day|
|+||Add 1000 Newbucks|
|-||Remove 1000 Newbucks|
|f12||Reset Achievement Progress|
|0||Award all personal upgrades (jetpack, energy, etc.)|
|9||Fill Vacpack with random items (How Rad slimes, Hunter Slimes, Prickle pears, Silver Parsnips and Oca Ocas were obtained in 0.2.0.)|