OK I am using Mozilla and this seems to work. This is your source code, but I set the width set in containerSlave to 75px .
This will work and does not look bad, but to be honest, you will need to use external code like JS (javascript). If you are open to this, I can show you a great trick to fix it.
.containerSlave { display: inline-flex; flex-direction: column; flex-wrap: wrap; margin: 2px 2px 2px 2px; padding: 2px 2px 2px 2px; height: 220px; **width:75px;** border: 2px solid red; } .containerSlave .ball { width: 20px; height: 20px; border-radius: 50%; line-height: 20px; text-align: center; text-shadow: 0 1px 1px #000; font-size: 15px; color: #ffffff; margin: 2px 2px 2px 2px; background: radial-gradient(circle at 20px 15px, #7FBBFC, #000); }
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