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HTML

              
                <!-- https://cras.sh/ -->

<!--打开下面这段注释代码-->
<div class="crassh">HOVER ME</div>
              
            
!

CSS

              
                .crassh {
    width: 200px;
    line-height: 200px;
    text-align: center;
    font-size: 32px;
    border: 1px solid #000;
    margin: 50px auto;
    /* border-width may be omitted by some engines if it doesn't have style(= not shown )                   */
    border-style: solid;
    
    
    cursor: pointer;

    &:hover,
    &:active{
        --initial-level-0: calc(1vh + 1% + 1px + 1em + 1vw + 1cm);
        /* Mixed constant */

        --level-1: calc(var(--initial-level-0) + var(--initial-level-0));
        /* 2 evaluations */

        --level-2: calc(var(--level-1) + var(--level-1));
        /* 4 evaluations */

        --level-3: calc(var(--level-2) + var(--level-2));
        /* 8 evaluations */

        --level-4: calc(var(--level-3) + var(--level-3));
        /* 16 evaluations */

        --level-5: calc(var(--level-4) + var(--level-4));
        /* 32 evaluations */

        --level-6: calc(var(--level-5) + var(--level-5));
        /* 64 evaluations */

        --level-7: calc(var(--level-6) + var(--level-6));
        /* 128 evaluations */

        --level-8: calc(var(--level-7) + var(--level-7));
        /* 256 evaluations */

        --level-9: calc(var(--level-8) + var(--level-8));
        /* 512 evaluations */

        --level-10: calc(var(--level-9) + var(--level-9));
        /* 1024 evaluations */

        --level-11: calc(var(--level-10) + var(--level-10));
        /* 2048 evaluations */

        --level-12: calc(var(--level-11) + var(--level-11));
        /* 4096 evaluations */

        --level-13: calc(var(--level-12) + var(--level-12));
        /* 8192 evaluations */

        --level-14: calc(var(--level-13) + var(--level-13));
        /* 16384 evaluations */

        --level-15: calc(var(--level-14) + var(--level-14));
        /* 32768 evaluations */

        --level-16: calc(var(--level-15) + var(--level-15));
        /* 65536 evaluations */

        --level-17: calc(var(--level-16) + var(--level-16));
        /* 131072 evaluations */

        --level-18: calc(var(--level-17) + var(--level-17));
        /* 262144 evaluations */

        --level-19: calc(var(--level-18) + var(--level-18));
        /* 524288 evaluations */

        --level-20: calc(var(--level-19) + var(--level-19));
        /* 1048576 evaluations */

        --level-21: calc(var(--level-20) + var(--level-20));
        /* 2097152 evaluations */

        --level-22: calc(var(--level-21) + var(--level-21));
        /* 4194304 evaluations */

        --level-23: calc(var(--level-22) + var(--level-22));
        /* 8388608 evaluations */

        --level-24: calc(var(--level-23) + var(--level-23));
        /* 16777216 evaluations */

        --level-25: calc(var(--level-24) + var(--level-24));
        /* 33554432 evaluations */

        --level-26: calc(var(--level-25) + var(--level-25));
        /* 67108864 evaluations */

        --level-27: calc(var(--level-26) + var(--level-26));
        /* 134217728 evaluations */

        --level-28: calc(var(--level-27) + var(--level-27));
        /* 268435456 evaluations */

        --level-29: calc(var(--level-28) + var(--level-28));
        /* 536870912 evaluations */

        --level-30: calc(var(--level-29) + var(--level-29));
        /* 1073741824 evaluations */

        --level-final: calc(var(--level-30) + 1px);
        /* 1073741824 evaluations */

        /* ^ these are not evaluated automatically in some engines -> we have to use them somewhere             */

        border-width: var(--level-final); /* <- use the computed value   */
    }
}
              
            
!

JS

              
                
              
            
!
999px

Console