I recommend providing dimensions for everything -- in detail. We might tend to assume too much. Besides, you know what you are talking about. (After that, I'd expect still more questions as those details become clearer.)

Yes, perhaps we can start a middle school version first: Children's Croquet Set Elastic Sponge Double Croquet Set Indoor and Outdoor Children's Training Rubber Foam Toy Suitable for Lawn, Backyard, Park, Etc amazon.com/Forevive-Childrens-Training-Suitable-Backyard/dp/‌​…

My grandmothor is being locked down in her nursing home, and can no longer play mahjong with her friends. So I am thinking of sending her a door ball training set, so she can play with her friend. Door Ball Newbie Training Set (Colour Anti Slip) - ¥66 detail.tmall.com/….

Or this as her 100th year birthday gift: (1) Long Life Brand Training Set - ¥100 item.taobao.com/… (2) Score Board/Hammer Set - ¥900 item.taobao.com/…

Spec of Croquet Ball and Gate Ball. I googled to find that Croquet ball is 9.3 cm diameter, weights 1 lb (454g), and gate ball 7.5 cm diameter, weighs 230g. So gateball suits old people better. And I guess cheapy weight sensors and low resolution ADC (8-bit Arduino built in ADC GPIO pin, MCP3008/10 bit, MCP3201 12 bit) should be more than enough.

And the OP might find the following Q&A useful for reference: Sensor to distinguish between different types of pegs on a pegboard electronics.stackexchange.com/questions/523764/…. In my answer, Ref 1 and Appendix A describe the cheapy weight sensor I have been using. Cheapy Weight Sensor: aliexpress.com/i/32669458593.html.

The OP might also like to consider the Load Cell approach. Some two years ago, I did a Micky Mouse toy project in weighing a growing plant. The spec is summarized below: (1) Weight range: 0g to 500g, (2) Accuracy < 1g, (3) Speed, 0.1s, (4) ADC, HX711, with Wheatstone bridge, (5) Rpi3B+ with MCP23017, ESP8266-12 WiFi, (6) LCD 20 characters x 4 lines characters. Ref: (7)raspberrypi.org/forums/….

Perhaps I should modify my plant weighting project hardware to the gateball training set, with automatic real time score record, directly transferred to my grandmother's smart phone.

Thanks all so far, so the Ball weighs approx 50g, so I’d need a sensor that can easily pickup the ball is resting in the “starting zone” the mat itself is 4 metres long and 1 metre wide with 1 goal (wicket) in the centre on the other end. At the end where the goal is, ideally we want to have multiple or a much larger load sensor to track where the ball comes to rest.

To continue So I guess we want to track the speed of the shot which might be calculated by connecting the start sensor and goals sensors, a timer between them can calculate speed. The reason for multiple sensors in the goal are is to track the accuracy. Would a load sensor/sensors be the right thing here,?

@MollyMal Actually I know almost nothing about the gateball rules, nor have seen any real games before . So I watched a couple of videos. My first impression is that the game is slow and boring, comparing the squash, my favourite sports.

@MollyMal Ah you might like to google YouTubes for ESP8266 to smart phone communication. I recommend NOT to watch any videos on ESP8266-01 because they are very out of date. Better watch those dated after 2018. If your project is year long with a couple of members, you might like to start with ESP32, which is more powerful than ESP8266-12. Cheers.