/* ── BACK TO TOP: MASTER STYLES ── */

.mt-btt {
    position: fixed;
    right: 40px;
    bottom: 40px;
    width: 54px;
    height: 54px;
    z-index: 1000;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all 0.5s cubic-bezier(0.16, 1, 0.3, 1);
    background: #fff;
    border-radius: 50%;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
}

.mt-btt.is-active {
    opacity: 1;
    visibility: visible;
}

.mt-btt-icon {
    position: relative;
    z-index: 5;
    transition: transform 0.3s ease;
    color: #000;
}

.mt-btt:hover .mt-btt-icon {
    transform: translateY(-3px);
}

/* STYLE 1: Progress Circle (Current Upgrade) */
.mt-btt-style-1 .mt-btt-progress-svg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.mt-btt-style-1 .mt-btt-progress-svg path {
    fill: none;
    stroke: var(--primary);
    stroke-width: 2;
    stroke-dasharray: 307.919, 307.919;
    stroke-dashoffset: 307.919;
    transition: stroke-dashoffset 10ms linear;
}

.mt-btt-style-1:hover {
    background: var(--primary);
}

.mt-btt-style-1:hover .mt-btt-icon {
    color: #fff;
}

/* STYLE 2: Minimalist Line */
.mt-btt-style-2 {
    background: transparent;
    box-shadow: none;
    flex-direction: column;
    height: 100px;
    width: 30px;
}

.mt-btt-line-wrapper {
    position: relative;
    width: 1px;
    height: 60px;
    background: rgba(0, 0, 0, 0.1);
    margin-bottom: 10px;
}

.mt-btt-line-progress {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 0%;
    background: var(--primary);
}

.mt-btt-style-2 .mt-btt-icon {
    width: 30px;
    height: 30px;
    background: #fff;
    border-radius: 50%;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    display: flex;
    align-items: center;
    justify-content: center;
}

/* STYLE 3: Glassmorphic Bubble */
.mt-btt-style-3 {
    background: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(15px);
    -webkit-backdrop-filter: blur(15px);
    border: 1px solid rgba(255, 255, 255, 0.3);
    width: 65px;
    height: 65px;
    padding: 10px;
}

.mt-btt-percentage {
    position: absolute;
    bottom: 8px;
    font-size: 10px;
    font-weight: 700;
    color: #000;
}

.mt-btt-style-3:hover {
    background: rgba(255, 255, 255, 0.4);
    transform: scale(1.1);
}

/* STYLE 4: Tech Square */
.mt-btt-style-4 {
    border-radius: 4px;
    background: #000;
    overflow: hidden;
}

.mt-btt-style-4 .mt-btt-icon {
    color: #fff;
}

.mt-btt-square-border {
    position: absolute;
    inset: 0;
    border: 2px solid var(--primary);
    clip-path: inset(100% 0 0 0); /* Bottom up fill */
    transition: clip-path 10ms linear;
}

.mt-btt-style-4:hover {
    background: var(--primary);
}

/* RESPONSIVE */
@media (max-width: 768px) {
    .mt-btt {
        right: 20px;
        bottom: 20px;
    }
}