It is Zhang Yuchen’s last summer break before high school, but events have taken an unwelcome turn — the 14-year-old’s game time has been decimated as China’s tech firms try to dispel accusations that they are selling “spiritual opium” to the country’s youth. An edict by gaming giant Tencent means that players aged 12 or younger can no longer make in-game purchases in multiplayer battle smash-hit Honor of Kings, while those aged 18 or younger are locked out after two hours during holidays and one hour on school nights. “I wanted to cry,” Zhang said as the news ricocheted across...