Electronic Entertainment - Chicken Dinner Airdrop Bomb (Tai Chi Bagua Cube)

This project was submitted to JLCPCB's "Electronic Fun" activity.
The hardware
        consists of two PCBs: a PUBG-themed airdrop shell PCB (with color silkscreen printing) and a timed "egg-exploding" PCB . The
"egg-exploding" PCB
        is powered by a 3.7V lithium battery. The main controller is an STM32F103C8T6. TouchCheck pads connect to the gold Tai Chi pads on the shell for touch button activation. After activation, a countdown is displayed on a digital tube (with a buzzer indicating the interval between seconds, and the buzzer becomes more rapid during the last 3 seconds). After 10 seconds, it "explodes" (the digital tube displays "hhhh," and a passive buzzer plays Canon music).
        The first version of the "egg-exploding" design used two CR2032 button batteries in series for power. However, it was later found that the button battery power supply current was only 10mA. During the verification process, the maximum operating current of the entire module was observed to be as high as 250mA using a student power supply, which was far from sufficient for the button batteries. Therefore, an iteration was carried out.
        The second version of the "egg-exploding" design uses a 3.7V lithium battery for power, which meets the current requirements and works successfully.
        Four 0-ohm resistors configure the touch chip's touch adjustment mode (OP1, OP2 set to high/low level). During actual soldering, select OP1=OP2=1, i.e., solder R11 and R13 (R12 and R14 are not soldered).
        The minimum system board can be removed for other projects when not in use. The blue cap
on the "PUBG Airdrop Shell PCB"
        is composed of a 3D-printed blue shoe cover fitted with a cut-out piece. If blue paint is available, it can also be sprayed blue.
        After April Fool's Day, it can be flipped over, with the yin-yang symbol facing outwards (as shown in the picture), for enhanced decorative appeal and long-term use.
The software (see appendix for software engineering) includes
        a passive buzzer driven by PWM via I/O ports, achieving different tones by adjusting the frequency;
        a common-cathode digital tube that displays numbers simply by setting the high and low levels of each pin;
        and a touch button reader—the I/O port reads a low level when the button is not pressed, a high level when the button is pressed, and a low level when the button is removed. This is achieved through three while loops to detect button presses.
However
        , while the original intention was for a compact and elegant design, the minimum system board used results in a relatively large size, making it difficult to fit the "exploding egg" (a reference to a specific device) into the casing.
        The battery connector lacks reverse connection protection; using a terminal block such as the XH2.54-2P can prevent reverse battery connection. [Please be extremely careful not to reverse the battery during DIY.]