/* ========================================
   BACK TO TOP BUTTON
   Item 62/78: Scroll to top functionality
   ======================================== */

/* ====================================
   BUTTON BASE
   ==================================== */

.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 56px;
    height: 56px;
    background: linear-gradient(135deg, var(--primary-color, #1565C0) 0%, #0d47a1 100%);
    color: white;
    border: none;
    border-radius: 50%;
    font-size: 24px;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px) scale(0.8);
    transition: all 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    z-index: 999;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3),
                0 8px 24px rgba(21, 101, 192, 0.4);
    display: flex;
    align-items: center;
    justify-content: center;
    backdrop-filter: blur(10px);
}

/* Icon */
.back-to-top::before {
    content: "↑";
    font-size: 28px;
    font-weight: bold;
}

/* ====================================
   VISIBLE STATE
   ==================================== */

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0) scale(1);
}

/* ====================================
   HOVER STATE
   ==================================== */

.back-to-top:hover {
    transform: translateY(-5px) scale(1.05);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.4),
                0 12px 32px rgba(21, 101, 192, 0.5);
    background: linear-gradient(135deg, #1976D2 0%, #1565C0 100%);
}

/* Bounce animation on hover */
.back-to-top:hover::before {
    animation: arrowBounce 0.6s ease infinite;
}

@keyframes arrowBounce {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-4px);
    }
}

/* ====================================
   ACTIVE STATE
   ==================================== */

.back-to-top:active {
    transform: translateY(-2px) scale(1);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

/* ====================================
   FOCUS VISIBLE
   ==================================== */

.back-to-top:focus-visible {
    outline: 3px solid #fff;
    outline-offset: 3px;
}

/* ====================================
   PROGRESS RING (optional)
   ==================================== */

.back-to-top-with-progress {
    position: relative;
}

.back-to-top-with-progress::after {
    content: '';
    position: absolute;
    top: -4px;
    left: -4px;
    right: -4px;
    bottom: -4px;
    border-radius: 50%;
    border: 3px solid transparent;
    border-top-color: var(--secondary-color, #00f2fe);
    transform: rotate(0deg);
    transition: transform 0.1s linear;
}

/* Progress based on scroll */
.back-to-top-with-progress[data-progress="25"]::after {
    transform: rotate(90deg);
}

.back-to-top-with-progress[data-progress="50"]::after {
    transform: rotate(180deg);
}

.back-to-top-with-progress[data-progress="75"]::after {
    transform: rotate(270deg);
}

.back-to-top-with-progress[data-progress="100"]::after {
    transform: rotate(360deg);
}

/* ====================================
   TOOLTIP
   ==================================== */

.back-to-top::after {
    content: attr(data-tooltip);
    position: absolute;
    right: calc(100% + 12px);
    top: 50%;
    transform: translateY(-50%);
    background: rgba(0, 0, 0, 0.9);
    color: white;
    padding: 8px 12px;
    border-radius: 6px;
    font-size: 14px;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.back-to-top:hover::after {
    opacity: 1;
}

/* Arrow for tooltip */
.back-to-top[data-tooltip]::before {
    position: relative;
    z-index: 1;
}

/* ====================================
   MOBILE RESPONSIVE
   ==================================== */

@media (max-width: 768px) {
    .back-to-top {
        width: 50px;
        height: 50px;
        bottom: 20px;
        right: 20px;
        font-size: 20px;
    }
    
    .back-to-top::before {
        font-size: 24px;
    }
    
    /* Hide tooltip on mobile */
    .back-to-top::after {
        display: none;
    }
}

/* ====================================
   THEME ADJUSTMENTS
   ==================================== */

/* Light theme */
[data-theme="light"] .back-to-top {
    background: linear-gradient(135deg, #1565C0 0%, #0d47a1 100%);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15),
                0 8px 24px rgba(21, 101, 192, 0.3);
}

[data-theme="light"] .back-to-top:hover {
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2),
                0 12px 32px rgba(21, 101, 192, 0.4);
}

/* ====================================
   VARIANTS
   ==================================== */

/* Emergency variant (red) */
.back-to-top.emergency {
    background: linear-gradient(135deg, #ff3b3b 0%, #d32f2f 100%);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3),
                0 8px 24px rgba(255, 59, 59, 0.4);
}

.back-to-top.emergency:hover {
    background: linear-gradient(135deg, #ff4b4b 0%, #e33f3f 100%);
}

/* Secondary variant (cyan) */
.back-to-top.secondary {
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3),
                0 8px 24px rgba(79, 172, 254, 0.4);
}

/* Minimal variant */
.back-to-top.minimal {
    background: rgba(255, 255, 255, 0.1);
    border: 2px solid rgba(255, 255, 255, 0.3);
    backdrop-filter: blur(10px);
}

.back-to-top.minimal:hover {
    background: rgba(255, 255, 255, 0.2);
    border-color: rgba(255, 255, 255, 0.5);
}

/* ====================================
   ALTERNATIVE ICONS
   ==================================== */

/* Chevron up */
.back-to-top.icon-chevron::before {
    content: "⌃";
    font-size: 32px;
}

/* Arrow circle */
.back-to-top.icon-circle::before {
    content: "⬆";
}

/* Rocket */
.back-to-top.icon-rocket::before {
    content: "🚀";
    font-size: 26px;
}

/* ====================================
   PULSE ANIMATION
   ==================================== */

.back-to-top.pulse {
    animation: buttonPulse 2s ease infinite;
}

@keyframes buttonPulse {
    0%, 100% {
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3),
                    0 8px 24px rgba(21, 101, 192, 0.4);
    }
    50% {
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3),
                    0 8px 24px rgba(21, 101, 192, 0.6),
                    0 0 0 10px rgba(21, 101, 192, 0.1);
    }
}

/* ====================================
   ACCESSIBILITY
   ==================================== */

/* High contrast mode */
@media (prefers-contrast: high) {
    .back-to-top {
        border: 3px solid white;
    }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    .back-to-top,
    .back-to-top::before,
    .back-to-top::after {
        transition: none;
        animation: none;
    }
    
    .back-to-top.visible {
        transform: none;
    }
}

/* ====================================
   PRINT
   ==================================== */

@media print {
    .back-to-top {
        display: none !important;
    }
}

/* ====================================
   POSITION VARIANTS
   ==================================== */

/* Bottom left */
.back-to-top.position-left {
    right: auto;
    left: 30px;
}

@media (max-width: 768px) {
    .back-to-top.position-left {
        left: 20px;
    }
}

/* Top right */
.back-to-top.position-top {
    bottom: auto;
    top: 30px;
}

/* ====================================
   SMOOTH SCROLL OVERRIDE
   ==================================== */

/* Ensure smooth scrolling is enabled */
html {
    scroll-behavior: smooth;
}

/* Scroll padding for fixed headers */
html {
    scroll-padding-top: 80px;
}