/* ========================================
   SKILLSET — STACK BY LAYERS
   The technologies are presented as the layers of a system, joined by
   a vertical "signal bus". Everything is visible at once (no carousel):
   - fixed-size logo cells → stable alignment from 320px to 2560px
   - label area reserves two lines → rows never misalign
   - core layers (APIs, Data, AI — the hero headline) get a gold node
   (header, divider and spacing: sections.css)
======================================== */

.stack {
    --bus-x: 9px;                                   /* bus position */
    --node: 11px;                                   /* node size */
    --label-col: clamp(220px, 22vw, 300px);         /* layer label column */
    --cell: clamp(84px, 3.5vw + 48px, 104px);       /* technology cell */
    --logo: clamp(40px, 1.6vw + 28px, 52px);        /* logo size */

    position: relative;
}

/* Vertical signal bus */
.stack-bus {
    position: absolute;
    top: 0;
    bottom: 0;
    left: var(--bus-x);
    width: 1px;
    background: linear-gradient(
        to bottom,
        rgba(var(--primary-rgb), 0.6),
        rgba(var(--primary-rgb), 0.12)
    );
    transform-origin: top center;
    pointer-events: none;
}

.stack-layers {
    display: flex;
    flex-direction: column;
    list-style: none;
}

/* ========================================
   LAYER ROW
======================================== */

.stack-layer {
    position: relative;
    display: grid;
    grid-template-columns: var(--label-col) minmax(0, 1fr);
    align-items: center;
    gap: 1.25rem 3rem;
    padding: 1.75rem 1rem 1.75rem calc(var(--bus-x) * 2 + 1.75rem);
    border-bottom: 1px solid var(--hairline);
    transition: background-color var(--transition-fast);
}

.stack-layer:first-child {
    border-top: 1px solid var(--hairline);
}

.stack-layer:hover {
    background: rgba(var(--primary-rgb), 0.03);
}

/* Node on the bus (diamond, like the experience highlights) */
.stack-layer::before {
    content: '';
    position: absolute;
    top: 50%;
    left: calc(var(--bus-x) - var(--node) / 2 + 0.5px);
    width: var(--node);
    height: var(--node);
    border: 1.5px solid var(--primary);
    background: var(--bg);
    transform: translateY(-50%) rotate(45deg);
    transition: background-color var(--transition-fast);
}

.stack-layer:hover::before {
    background: var(--primary);
}

/* Core layers: the ones named in the hero headline */
.stack-layer.is-core::before {
    border-color: var(--secondary);
    background: var(--secondary-fill);
    box-shadow: 0 0 0 3px rgba(var(--secondary-rgb), 0.15);
}

/* ========================================
   LAYER LABEL
======================================== */

.stack-layer-label {
    display: grid;
    gap: 0.3rem;
    min-width: 0;
}

.stack-layer-index {
    color: var(--text-subtle);
    font-family: var(--font-tech);
    font-size: 0.85rem;
    font-weight: 700;
    letter-spacing: 0.15em;
}

.stack-layer.is-core .stack-layer-index {
    color: var(--secondary);
}

.stack-layer-title {
    color: var(--text-strong);
    font-family: var(--font-display);
    font-size: clamp(1rem, 0.9rem + 0.35vw, 1.2rem);
    font-weight: 700;
    line-height: 1.3;
    letter-spacing: 0.01em;
}

.stack-layer-desc {
    color: var(--text-muted);
    font-size: 0.85rem;
    line-height: 1.5;
}

/* ========================================
   TECHNOLOGIES (fixed-size cells)
======================================== */

.stack-layer-techs {
    display: grid;
    grid-template-columns: repeat(auto-fill, var(--cell));
    justify-content: start;
    gap: 0.75rem;
    list-style: none;
}

.stack-tech {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.55rem;
    min-width: 0;
    text-align: center;
}

.stack-tech img {
    width: var(--logo);
    height: var(--logo);
    object-fit: contain;
    transition:
        transform var(--transition-fast),
        filter var(--transition-fast);
}

/* Two lines reserved for every label: rows stay aligned even when a
   name wraps on small screens */
.stack-tech span {
    min-height: 2.6em;
    color: var(--text);
    font-size: 0.75rem;
    font-weight: 600;
    line-height: 1.3;
    overflow-wrap: anywhere;
    transition: color var(--transition-fast);
}

/* Hover: transform/filter only (no layout change) */
.stack-tech:hover img {
    transform: translateY(-3px);
    filter: drop-shadow(0 0 8px rgba(var(--primary-rgb), 0.28));
}

.stack-tech:hover span {
    color: var(--primary);
}

/* ========================================
   LOGO TREATMENT PER THEME
======================================== */

/* Dark logos (Prisma, AWS, MySQL, SQL Server): rendered light on the dark UI,
   original colours in the light theme */
.stack-tech img.logo-invert {
    filter: brightness(0) invert(0.95);
}

.stack-tech:hover img.logo-invert {
    filter: brightness(0) invert(0.95) drop-shadow(0 0 8px rgba(var(--primary-rgb), 0.28));
}

:root[data-theme="light"] .stack-tech img.logo-invert {
    filter: none;
}

:root[data-theme="light"] .stack-tech:hover img.logo-invert {
    filter: drop-shadow(0 0 8px rgba(var(--primary-rgb), 0.28));
}

/* White-only logos (Express.js, GitHub): dark counterparts in light theme */
:root[data-theme="light"] .stack-tech img.logo-on-dark {
    filter: brightness(0);
}

:root[data-theme="light"] .stack-tech:hover img.logo-on-dark {
    filter: brightness(0) drop-shadow(0 0 8px rgba(var(--primary-rgb), 0.28));
}

/* White logo on a plate (OpenAI): the plate only shows in light theme */
.stack-tech img.logo-plate {
    border-radius: 50%;
    background: var(--logo-plate);
}

:root[data-theme="light"] .stack-tech img.logo-plate {
    padding: 8px;
}

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

/* Tablet: label above the technologies */
@media (max-width: 1023px) {
    .stack-layer {
        grid-template-columns: 1fr;
        align-items: start;
        gap: 1rem;
    }

    /* Node aligned with the layer index line */
    .stack-layer::before {
        top: calc(1.75rem + 0.45rem);
        transform: rotate(45deg);
    }
}

/* Mobile */
@media (max-width: 600px) {
    .stack {
        --bus-x: 7px;
        --node: 10px;
        --cell: 84px;
    }

    .stack-layer {
        padding: 1.5rem 0 1.5rem calc(var(--bus-x) * 2 + 1.25rem);
    }

    .stack-layer::before {
        top: calc(1.5rem + 0.45rem);
    }

    .stack-layer-techs {
        gap: 0.5rem;
    }
}

/* Small phones: three cells per row still fit in 288px */
@media (max-width: 400px) {
    .stack {
        --cell: 76px;
        --logo: 40px;
    }

    .stack-layer-techs {
        gap: 0.4rem;
    }

    .stack-tech span {
        font-size: 0.72rem;
    }
}

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

@media (prefers-reduced-motion: reduce) {
    .stack-tech:hover img {
        transform: none;
    }
}

/* Touch devices: no sticky hover lift */
@media (hover: none) {
    .stack-tech:hover img {
        transform: none;
    }
}