As can you see the problem is that when you open a text box a virtual keyboard just covers the box were player is going to write. How to make that i should move when keyboard is opened.
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You can scroll your layout up when the textbox is edited. The problem with textbox object is that you don't know for sure when mobile keyboard is on the screen. You can try this addon, it has "on focused" and "on unfocused" events:
construct.net/en/forum/extending-construct-2/addons-29/behavior-textbox-122609
Another solution would be making your own text box and keyboard:
scirra.com/tutorials/739/your-own-textbox
scirra.com/tutorials/1153/mobile-keyboard-and-hall-of-fame-for-all-mobile-devices