2D Cash Register Simulator Preferably in Unreal

I need the core logic of a 2-D cash-machine training game built in Unreal Engine (paper2D is fine). The whole focus right now is mechanical accuracy, not visuals, so placeholder sprites, boxes or rectangles are all that’s required.

Gameplay flow
• A customer appears with a basket of items (expect multiple-item purchases every time).
• Their total is displayed in pounds and pence.
• The player clicks notes and coins laid out on screen to build the amount tendered, then clicks again to choose the change to hand back. Drag-and-drop or keyboard entry could be added later, but click-to-select is essential for this prototype.
• When the player confirms, your code checks the transaction. If the change is mathematically perfect the session continues; any mistake triggers an immediate “game over” screen.

Key requirements
– Absolute accuracy of change calculation for all standard UK denominations (£50-£5 notes, £2-1 coins, 50p-1p).
– Efficient algorithm that copes with limited quantities of each denomination and still finds a correct combination when one exists.
– Clean, commented Blueprints (or C++ if you prefer) so I can expand visuals later.
– Simple UI widgets: item list with prices, running subtotal, cash palette, change palette, confirmation button, and a restart button after failure.

Acceptance criteria
1. Compile-ready Unreal project opens without errors in the latest UE5 release.
2. A playable loop that supports at least ten successive customer transactions.
3. Automatic validation confirms correct or incorrect change every time.
4. No art beyond primitive shapes; code clearly separated from visual assets.

Once this core is solid I’ll handle graphics and sound, so keep the structure flexible for future polish.

Looking forward to seeing your approach to elegant, airtight currency logic in Unreal.