First time I've heard of someone getting stuck at the beginning of level 2 😅. Though if you're to give it another shot, look at the controls in the pause menu(ESC). You can pick it up through the window.
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Wait, so you're not able to pick up the cube by right-clicking? I've seen plenty of people play it and that never happened. I'm a bit confused.
Edit- Or are you talking about not knowing how to get it out after picking it up? There's a small gap to the right that you can pass the cube through, if that helps.