One stage takes one to three minutes. No sign-up, no download.
The two play very differently. Credit Rush runs on a single track and asks only that you move your finger left or right, so it is the easier one to pick up first. Deadline Defense has you grab gears and place them around a circular board, deciding what goes where, so it asks for a little more thought. Both run five stages, and a stage takes one to three minutes.
Just a browser. They are free, and there is no account to create and nothing to install. They run on phones and on computers. Both are built around touch, so a phone is the better fit. Hold it upright.
Cleared stages and best scores are stored inside your own browser. Nothing is sent to a server, so progress does not carry across to another device or another browser, and clearing your browser data clears the record too. If you close a stage partway through, that stage starts again from the beginning.
Everything here is a standalone game that finishes on its own. The same characters appear, but the main game, Unit Survival, is a simulation where you steer a fifteen-week term through your choices — a different thing to play. Nothing you do in a mini game carries into it.