In dropdown enter the following code to activate "Beat This Level" Mode: icandoit

Ghost Mode
During game play press ~ (tilde) to activate a dropdown menu.

In dropdown enter the following code to activate Ghost mode: ghost

Invulnerability
During game play press ~ (tilde) to activate a dropdown menu.

In dropdown enter the following code for Invulnerability: xgod

Learnin' to Fly
During game play press ~ (tilde) to activate a dropdown menu.

In dropdown enter the following code to Fly: fly

Level Upgrades
During game play press ~ (tilde) to activate a dropdown menu.

In dropdown enter the following code to bring all levels to upgrade level 1: upgrademe 1 (same works with 2, 3, 4 - do "upgrademe 4" to max everything out)

Open All Levels
During game play press ~ (tilde) to activate a dropdown menu.

In dropdown enter the following code to Open Levels = open map00 (number between 00 and 40)

Return to Normal
During game play press ~ (tilde) to activate a dropdown menu.