/*css/atom_builder.css*/
/* =========================================================
   BUILD AN ATOM
   ========================================================= */

.atom-builder-layout {
    width: 100%;
    padding: 18px 0 60px;
}


/* =========================================================
   HEADER
   ========================================================= */

.atom-builder-header {
    display: flex;
    justify-content: space-between;
    gap: 24px;
    align-items: flex-end;

    margin-bottom: 24px;
}

.atom-builder-header h1 {
    margin: 6px 0 8px;

    color: #fff;
    font-size: clamp(2.4rem, 5vw, 4.4rem);
    line-height: 1;
}

.atom-builder-header p {
    margin: 0;

    max-width: 680px;

    color: var(--color-text-muted);
    line-height: 1.55;
}

.atom-builder-eyebrow,
.atom-builder-small-label {
    color: var(--color-accent);

    font-size: 0.72rem;
    font-weight: 800;
    letter-spacing: 0.15em;
}


/* =========================================================
   MAIN GRID
   ========================================================= */

.atom-builder-grid {
    display: grid;

    grid-template-columns:
        260px
        minmax(500px, 1fr)
        240px;

    gap: 20px;

    align-items: start;
}

.atom-builder-left,
.atom-builder-right {
    display: flex;
    flex-direction: column;
    gap: 16px;
}


/* =========================================================
   CARDS
   ========================================================= */

.atom-builder-picker-card,
.atom-builder-selected-card,
.atom-builder-electron-card,
.atom-builder-progress-card {
    border: 1px solid rgba(220, 180, 140, 0.28);
    border-radius: 16px;

    background: rgba(26, 20, 17, 0.86);

    padding: 16px;
}


/* =========================================================
   ELEMENT PICKER
   ========================================================= */

.atom-builder-picker-card label {
    display: block;

    margin-bottom: 7px;

    color: var(--color-text);
    font-size: 13px;
    font-weight: 700;
}

#atomBuilderGroupSelect {
    width: 100%;

    padding: 9px 10px;

    border: 1px solid rgba(220, 180, 140, 0.42);
    border-radius: 9px;

    background: rgba(8, 8, 8, 0.55);
    color: var(--color-text);

    font-size: 14px;
}

.atom-builder-element-choices {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));

    gap: 7px;

    margin-top: 14px;
}

.atom-builder-element-choice {
    min-height: 46px;

    border: 1px solid rgba(255, 255, 255, 0.12);
    border-radius: 8px;

    background: rgba(255, 255, 255, 0.055);
    color: #fff;

    cursor: pointer;

    font-size: 14px;
    font-weight: 700;
}

.atom-builder-element-choice:hover {
    border-color: rgba(238, 172, 96, 0.8);
    background: rgba(238, 172, 96, 0.12);
}

.atom-builder-element-choice.selected {
    border-color: var(--color-accent);
    background: rgba(238, 172, 96, 0.22);
    color: #ffd39a;
}


/* =========================================================
   SELECTED ELEMENT TILE
   ========================================================= */

.atom-builder-element-tile {
    position: relative;

    min-height: 180px;

    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;

    border: 1px solid rgba(238, 172, 96, 0.45);
    border-radius: 14px;

    background:
        radial-gradient(
            circle at center,
            rgba(238, 172, 96, 0.16),
            transparent 65%
        ),
        rgba(5, 5, 5, 0.4);
}

.atom-builder-symbol {
    color: #fff;

    font-size: 60px;
    font-weight: 800;
    line-height: 1;
}

.atom-builder-element-name {
    margin-top: 8px;

    color: var(--color-text-muted);
    font-size: 14px;
}

/* =========================================================
   ELEMENT TILE NUMBERS
   ========================================================= */

.atom-builder-atomic-number-info {
    position: relative;

    padding: 3px 8px;

    border: 0;
    border-radius: 7px;

    background: transparent;
    color: #ffd39a;

    font: inherit;
    font-size: 17px;
    font-weight: 800;

    cursor: help;
}


/* Nucleon number above the symbol */

.atom-builder-mass-number {
    margin-bottom: 10px;
}


/* Proton number below the element name */

.atom-builder-proton-number {
    margin-top: 10px;
}


/* Small hover/click highlight */

.atom-builder-atomic-number-info:hover,
.atom-builder-atomic-number-info:focus-visible,
.atom-builder-atomic-number-info.show-tooltip {
    background: rgba(238, 172, 96, 0.12);
    outline: 1px solid rgba(238, 172, 96, 0.35);
}


/* Tooltip */

.atom-builder-atomic-number-info::after {
    content: attr(data-tooltip);

    position: absolute;

    left: 50%;
    bottom: calc(100% + 8px);

    transform: translateX(-50%) translateY(4px);

    min-width: max-content;

    padding: 6px 9px;

    border: 1px solid rgba(238, 172, 96, 0.45);
    border-radius: 7px;

    background: rgba(20, 14, 11, 0.98);
    color: #fff;

    font-size: 11px;
    font-weight: 600;
    line-height: 1.2;

    opacity: 0;
    visibility: hidden;
    pointer-events: none;

    z-index: 20;

    transition:
        opacity 0.15s ease,
        transform 0.15s ease,
        visibility 0.15s ease;
}


/* Little tooltip arrow */

.atom-builder-atomic-number-info::before {
    content: "";

    position: absolute;

    left: 50%;
    bottom: calc(100% + 3px);

    transform: translateX(-50%);

    border: 5px solid transparent;
    border-top-color: rgba(238, 172, 96, 0.45);

    opacity: 0;
    visibility: hidden;

    z-index: 21;
}


.atom-builder-atomic-number-info:hover::after,
.atom-builder-atomic-number-info:hover::before,
.atom-builder-atomic-number-info:focus-visible::after,
.atom-builder-atomic-number-info:focus-visible::before,
.atom-builder-atomic-number-info.show-tooltip::after,
.atom-builder-atomic-number-info.show-tooltip::before {
    opacity: 1;
    visibility: visible;
}

.atom-builder-atomic-number-info:hover::after,
.atom-builder-atomic-number-info:focus-visible::after,
.atom-builder-atomic-number-info.show-tooltip::after {
    transform: translateX(-50%) translateY(0);
}

.atom-builder-proton-number::after {
    top: calc(100% + 8px);
    bottom: auto;
}

.atom-builder-proton-number::before {
    top: calc(100% + 3px);
    bottom: auto;

    border-top-color: transparent;
    border-bottom-color: rgba(238, 172, 96, 0.45);
}

.atom-builder-feedback {
    display: grid;
    grid-template-columns: auto 1fr;
    align-items: stretch;

    margin-top: 16px;

    border: 1px solid rgba(255, 177, 88, 0.18);
    border-radius: 14px;

    background:
        linear-gradient(
            90deg,
            rgba(255, 157, 55, 0.09),
            rgba(255, 157, 55, 0.025)
        );

    overflow: hidden;
}


/* Electron configuration result */

.atom-builder-configuration-display {
    min-width: 190px;

    padding: 16px 22px;

    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 5px;

    border-right: 1px solid rgba(255, 177, 88, 0.18);

    background: rgba(255, 153, 51, 0.06);
}


.atom-builder-configuration-label {
    font-size: 0.72rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;

    color: #ffb45f;
}


.atom-builder-configuration-value {
    font-size: 1.75rem;
    line-height: 1;
    color: #ffffff;
}


/* Existing instruction/message area */

.atom-builder-feedback .atom-builder-message {
    margin: 0;

    display: flex;
    align-items: center;

    padding: 18px 22px;

    border: 0;
    border-radius: 0;

    background: transparent;
}

.atom-builder-composition {
    display: grid;

    grid-template-columns: repeat(3, 1fr);

    gap: 8px;

    margin-top: 16px;
}

.atom-builder-composition div {
    min-width: 0;

    padding: 9px 5px;

    text-align: center;

    border-radius: 9px;

    background: rgba(255, 255, 255, 0.045);
}

.atom-builder-composition span {
    display: block;

    margin-bottom: 5px;

    color: var(--color-text-muted);
    font-size: 10px;
}

.atom-builder-composition strong {
    color: #fff;
    font-size: 18px;
}


/* =========================================================
   ATOM WORKSPACE
   ========================================================= */

.atom-builder-workspace {
    min-width: 0;

    padding: 18px;

    border: 1px solid rgba(238, 172, 96, 0.25);
    border-radius: 20px;

    background:
        radial-gradient(
            circle at center,
            rgba(238, 120, 35, 0.10),
            transparent 58%
        ),
        rgba(10, 8, 7, 0.55);
}

.atom-builder-workspace-header {
    display: flex;

    justify-content: space-between;
    align-items: flex-start;

    gap: 20px;

    min-height: 66px;
}

.atom-builder-workspace-header h2 {
    margin: 5px 0 0;

    color: #fff;
    font-size: 20px;
}

.atom-builder-shell-counter {
    padding: 7px 11px;

    border: 1px solid rgba(238, 172, 96, 0.4);
    border-radius: 999px;

    color: #ffd39a;
    background: rgba(238, 172, 96, 0.08);

    font-size: 12px;
    font-weight: 700;
}


/* =========================================================
   ATOM STAGE
   ========================================================= */

.atom-builder-stage {
    position: relative;

    width: min(100%, 620px);
    aspect-ratio: 1 / 1;

    margin: 10px auto;

    overflow: hidden;

    border-radius: 50%;

    user-select: none;
}

.atom-builder-stage.drag-over {
    background: rgba(238, 172, 96, 0.035);
}


/* rings */

.atom-builder-ring {
    position: absolute;

    left: 50%;
    top: 50%;

    transform: translate(-50%, -50%);

    border: 2px solid rgba(255, 255, 255, 0.19);
    border-radius: 50%;

    pointer-events: none;
}

.atom-builder-ring.complete {
    border-color: rgba(255, 255, 255, 0.34);
}

.atom-builder-ring.active {
    border-color: rgba(238, 172, 96, 0.95);

    box-shadow:
        0 0 10px rgba(238, 172, 96, 0.18),
        inset 0 0 10px rgba(238, 172, 96, 0.05);
}


/* nucleus */

.atom-builder-nucleus {
    position: absolute;

    left: 50%;
    top: 50%;

    transform: translate(-50%, -50%);

    width: 112px;
    height: 112px;

    display: flex;
    flex-direction: column;

    align-items: center;
    justify-content: center;

    gap: 5px;

    border: 2px solid rgba(238, 172, 96, 0.8);
    border-radius: 50%;

    background:
        radial-gradient(
            circle at 40% 35%,
            rgba(238, 172, 96, 0.28),
            rgba(40, 23, 15, 0.96)
        );

    color: #fff;

    z-index: 5;
}

.atom-builder-nucleus strong {
    font-size: 15px;
}


/* placed electrons */

.atom-builder-placed-electron {
    position: absolute;

    width: 18px;
    height: 18px;

    transform: translate(-50%, -50%);

    display: flex;

    align-items: center;
    justify-content: center;

    border-radius: 50%;

    background: #f3b567;
    color: #1a1009;

    font-size: 9px;
    font-weight: 900;

    box-shadow: 0 0 10px rgba(238, 172, 96, 0.4);

    z-index: 4;
}

.atom-builder-placed-electron {
    cursor: pointer;
}

.atom-builder-placed-electron:hover {
    transform: translate(-50%, -50%) scale(1.2);
}

.atom-builder-placed-electron:hover::after {
    content: "×";
    position: absolute;
    top: -18px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 14px;
    font-weight: 700;
}

/* =========================================================
   ISOTOPE PICKER
   ========================================================= */

.atom-builder-isotope-picker {
    margin-top: 14px;
    padding: 12px;

    border: 1px solid rgba(238, 172, 96, 0.22);
    border-radius: 10px;

    background: rgba(255, 255, 255, 0.035);
}

.atom-builder-isotope-picker label {
    display: block;

    margin-bottom: 7px;

    color: var(--color-text-muted);

    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

#atomBuilderIsotopeSelect {
    width: 100%;

    padding: 8px 9px;

    border: 1px solid rgba(238, 172, 96, 0.38);
    border-radius: 8px;

    background: rgba(8, 8, 8, 0.55);
    color: #fff;

    font-size: 13px;
}

.atom-builder-isotope-description {
    margin-top: 8px;

    color: #ffd39a;

    font-size: 11px;
    line-height: 1.4;
}

/* =========================================================
   ELECTRON SOURCE
   ========================================================= */

.atom-builder-electron-card p {
    color: var(--color-text-muted);
    line-height: 1.45;
}

.atom-builder-electron-source {
    width: 76px;
    height: 76px;

    margin: 18px auto;

    display: flex;

    align-items: center;
    justify-content: center;

    border: 2px solid rgba(238, 172, 96, 0.8);
    border-radius: 50%;

    background:
        radial-gradient(
            circle at 35% 30%,
            #ffd59c,
            #d88939
        );

    color: #24150b;

    font-size: 29px;
    font-weight: 800;

    cursor: grab;
}

.atom-builder-electron-source:active {
    cursor: grabbing;
}

.atom-builder-accessible-add {
    width: 100%;
}

.atom-builder-electron-card small {
    display: block;

    margin-top: 8px;

    color: rgba(214, 202, 190, 0.6);

    text-align: center;
}


/* =========================================================
   CHARGE / PROGRESS
   ========================================================= */

.atom-builder-charge-equation {
    margin-top: 12px;

    color: #fff;

    font-size: 20px;
    font-weight: 700;

    text-align: center;
}

.atom-builder-charge-description {
    margin-top: 8px;

    color: var(--color-text-muted);

    font-size: 12px;
    text-align: center;
}

.atom-builder-progress-track {
    height: 8px;

    margin: 18px 0 8px;

    overflow: hidden;

    border-radius: 999px;

    background: rgba(255, 255, 255, 0.08);
}

.atom-builder-progress-bar {
    width: 0%;
    height: 100%;

    border-radius: inherit;

    background: var(--color-accent);

    transition: width 0.25s ease;
}

#atomBuilderTotalProgress {
    color: var(--color-text-muted);

    font-size: 12px;

    text-align: center;
}

/* =========================================================
   USES OF ISOTOPES
   ========================================================= */

.atom-builder-isotope-uses {
    margin-top: 70px;
    padding-top: 50px;

    border-top: 1px solid rgba(238, 172, 96, 0.18);
}


/* ---------------------------------------------------------
   Heading
   --------------------------------------------------------- */

.atom-builder-isotope-uses-heading {
    max-width: 760px;

    margin-bottom: 28px;
}

.atom-builder-isotope-uses-heading h2 {
    margin: 7px 0 12px;

    color: #fff;

    font-size: clamp(2rem, 4vw, 3.3rem);
    line-height: 1.05;
}

.atom-builder-isotope-uses-heading p {
    margin: 0;

    color: var(--color-text-muted);

    font-size: 15px;
    line-height: 1.65;
}


/* ---------------------------------------------------------
   Main isotope concept
   --------------------------------------------------------- */

.atom-builder-isotope-concept {
    display: grid;

    grid-template-columns: 110px 1fr;

    gap: 22px;

    align-items: center;

    margin-bottom: 28px;
    padding: 22px;

    border: 1px solid rgba(238, 172, 96, 0.32);
    border-radius: 16px;

    background:
        linear-gradient(
            120deg,
            rgba(238, 172, 96, 0.11),
            rgba(255, 255, 255, 0.025)
        );
}

.atom-builder-isotope-concept-symbol {
    display: flex;

    align-items: center;
    justify-content: center;

    min-height: 90px;

    border-right: 1px solid rgba(238, 172, 96, 0.22);

    color: var(--color-accent);

    font-size: 45px;
    font-weight: 800;
}

.atom-builder-isotope-concept-symbol sup {
    margin-right: 2px;

    font-size: 18px;
}

.atom-builder-isotope-concept strong {
    color: #fff;

    font-size: 17px;
}

.atom-builder-isotope-concept p {
    margin: 7px 0 0;

    max-width: 800px;

    color: var(--color-text-muted);

    font-size: 13px;
    line-height: 1.6;
}


/* ---------------------------------------------------------
   Uses grid
   --------------------------------------------------------- */

.atom-builder-isotope-use-grid {
    display: grid;

    grid-template-columns:
        repeat(4, minmax(0, 1fr));

    gap: 14px;
}


/* Individual use */

.atom-builder-isotope-use-card {
    position: relative;

    min-height: 230px;

    padding: 18px;

    overflow: hidden;

    border: 1px solid rgba(255, 255, 255, 0.11);
    border-radius: 15px;

    background:
        radial-gradient(
            circle at 100% 0%,
            rgba(238, 172, 96, 0.10),
            transparent 45%
        ),
        rgba(20, 16, 14, 0.82);

    transition:
        transform 0.18s ease,
        border-color 0.18s ease,
        background 0.18s ease;
}

.atom-builder-isotope-use-card:hover {
    transform: translateY(-3px);

    border-color: rgba(238, 172, 96, 0.55);

    background:
        radial-gradient(
            circle at 100% 0%,
            rgba(238, 172, 96, 0.16),
            transparent 48%
        ),
        rgba(25, 19, 16, 0.88);
}


/* Field name */

.atom-builder-isotope-field {
    display: inline-block;

    padding: 4px 8px;

    border: 1px solid rgba(238, 172, 96, 0.28);
    border-radius: 999px;

    color: #ffc27d;

    font-size: 9px;
    font-weight: 800;
    letter-spacing: 0.1em;
}

/* ---------------------------------------------------------
   Isotope use illustrations
   --------------------------------------------------------- */

/* ---------------------------------------------------------
   Isotope use images
   --------------------------------------------------------- */

.atom-builder-isotope-image {
    position: absolute;

    top: 18px;
    right: 18px;

    width: 125px;
    height: 105px;

    overflow: hidden;

    border-radius: 11px;

    background: rgba(0, 0, 0, 0.25);
}


/* Image itself */
.atom-builder-isotope-image img {
    width: 100%;
    height: 100%;

    display: block;

    object-fit: cover;

    /*
     * Change these variables on individual images
     * to control which part of the photo is visible.
     */
    object-position:
        var(--crop-x, 50%)
        var(--crop-y, 50%);

    /*
     * Optional extra zoom for stronger cropping.
     */
    transform: scale(var(--crop-zoom, 1));

    transition: transform 0.25s ease;
}


/* Small dark gradient so caption stays readable */
.atom-builder-isotope-image::after {
    content: "";

    position: absolute;
    inset: 45% 0 0;

    background:
        linear-gradient(
            to bottom,
            transparent,
            rgba(0, 0, 0, 0.82)
        );

    pointer-events: none;
}


/* Image caption */
.atom-builder-isotope-image > span {
    position: absolute;

    left: 8px;
    right: 8px;
    bottom: 7px;

    z-index: 2;

    color: #fff;

    font-size: 8px;
    font-weight: 700;

    letter-spacing: 0.07em;
    text-transform: uppercase;

    text-shadow: 0 1px 4px rgba(0, 0, 0, 0.9);
}


/* Caption inside illustration */

.atom-builder-isotope-graphic > span {
    position: absolute;

    left: 50%;
    bottom: 2px;

    transform: translateX(-50%);

    width: max-content;

    color: rgba(255, 211, 154, 0.72);

    font-size: 8px;
    font-weight: 700;

    letter-spacing: 0.07em;
    text-transform: uppercase;
}

/* Large isotope notation */

.atom-builder-use-isotope {
    margin-top: 20px;

    color: #fff;

    font-size: 41px;
    font-weight: 800;
    line-height: 1;
}

.atom-builder-use-isotope sup {
    position: relative;

    top: -0.7em;

    margin-right: 2px;

    color: var(--color-accent);

    font-size: 15px;
}


/* Card text */

.atom-builder-isotope-use-card h3 {
    margin: 12px 0 7px;

    color: #ffd39a;

    font-size: 16px;
}

.atom-builder-isotope-use-card p {
    margin: 0;

    color: var(--color-text-muted);

    font-size: 12px;
    line-height: 1.55;
}


/* ---------------------------------------------------------
   Safety / conclusion
   --------------------------------------------------------- */

.atom-builder-isotope-safety-note {
    margin-top: 18px;

    padding: 16px 19px;

    border-left: 3px solid var(--color-accent);

    background: rgba(238, 172, 96, 0.055);
}

.atom-builder-isotope-safety-note strong {
    color: #fff;
}

.atom-builder-isotope-safety-note p {
    margin: 5px 0 0;

    color: var(--color-text-muted);

    font-size: 12px;
    line-height: 1.55;
}

/* =========================================================
   NUCLEUS BUILDER
   ========================================================= */

.nucleus-builder {
    margin-top: 70px;
    padding-top: 50px;

    border-top:
        1px solid rgba(238, 172, 96, 0.18);
}


.nucleus-builder-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;

    gap: 24px;

    margin-bottom: 24px;
}


.nucleus-builder-header h2 {
    margin: 6px 0 8px;

    color: #fff;

    font-size: clamp(2rem, 4vw, 3.3rem);
    line-height: 1.05;
}


.nucleus-builder-header p {
    max-width: 700px;

    margin: 0;

    color: var(--color-text-muted);

    line-height: 1.55;
}


/* =========================================================
   GRID
   ========================================================= */

.nucleus-builder-grid {
    display: grid;

    grid-template-columns:
        230px
        minmax(360px, 1fr)
        260px;

    gap: 18px;

    align-items: stretch;
}


.nucleus-builder-card {
    min-width: 0;

    padding: 18px;

    border:
        1px solid rgba(238, 172, 96, 0.25);

    border-radius: 16px;

    background:
        rgba(20, 15, 12, 0.82);
}


/* =========================================================
   CONTROLS
   ========================================================= */

.nucleus-builder-controls {
    display: flex;
    flex-direction: column;

    gap: 18px;
}


.nucleus-builder-control {
    padding-top: 14px;

    border-top:
        1px solid rgba(255, 255, 255, 0.08);
}


.nucleus-builder-control-heading {
    display: flex;
    justify-content: space-between;
    align-items: center;

    gap: 10px;

    margin-bottom: 10px;
}


.nucleus-builder-control-heading strong {
    display: block;

    color: #fff;

    font-size: 14px;
}


.nucleus-builder-control-heading small {
    display: block;

    margin-top: 2px;

    color: var(--color-text-muted);

    font-size: 10px;
}


.nucleus-builder-stepper {
    display: grid;

    grid-template-columns:
        42px
        minmax(0, 1fr)
        42px;

    gap: 6px;
}


.nucleus-builder-stepper button,
.nucleus-builder-stepper input {
    height: 42px;

    border:
        1px solid rgba(238, 172, 96, 0.32);

    border-radius: 8px;

    background:
        rgba(8, 8, 8, 0.55);

    color: #fff;

    text-align: center;
}


.nucleus-builder-stepper button {
    cursor: pointer;

    color: #ffd39a;

    font-size: 21px;
    font-weight: 700;
}


.nucleus-builder-stepper button:hover {
    border-color: var(--color-accent);

    background:
        rgba(238, 172, 96, 0.12);
}


.nucleus-builder-stepper input {
    width: 100%;

    font-size: 18px;
    font-weight: 800;
}


/*
 * Remove browser's large number arrows because
 * the activity already has + / − buttons.
 */

.nucleus-builder-stepper input::-webkit-inner-spin-button,
.nucleus-builder-stepper input::-webkit-outer-spin-button {
    margin: 0;

    -webkit-appearance: none;
}


.nucleus-builder-equation {
    margin-top: 18px;
}

.nucleus-builder-controls,
.nucleus-builder-result {
    align-self: start;
    height: auto;
}

.nucleus-builder-result {
    gap: 14px;
}

.nucleus-builder-stability-text {
    margin-top: 0;
}

.nucleus-builder-equation span,
.nucleus-builder-equation small {
    display: block;

    color: var(--color-text-muted);

    font-size: 10px;
}


.nucleus-builder-equation strong {
    display: block;

    margin: 5px 0;

    color: #fff;

    font-size: 23px;
}


/* =========================================================
   PARTICLE COLOURS
   ========================================================= */

.nucleus-builder-particle-key {
    display: inline-block;

    width: 12px;
    height: 12px;

    flex: 0 0 auto;

    border-radius: 50%;
}


.nucleus-builder-particle-key.proton,
.nucleus-builder-particle.proton {
    background: #db5548;
}


.nucleus-builder-particle-key.neutron,
.nucleus-builder-particle.neutron {
    background: #5686c5;
}


/* =========================================================
   NUCLEUS VISUAL
   ========================================================= */

.nucleus-builder-visual {
    display: flex;
    flex-direction: column;
}


.nucleus-builder-visual-header {
    display: flex;

    justify-content: space-between;
    align-items: flex-start;

    gap: 16px;
}


.nucleus-builder-visual-header h3 {
    margin: 5px 0 0;

    color: #fff;

    font-size: 20px;
}


.nucleus-builder-stage {
    position: relative;

    width: min(100%, 360px);
    aspect-ratio: 1;

    margin: 20px auto;

    overflow: hidden;

    border-radius: 50%;

    background:
        radial-gradient(
            circle,
            rgba(255, 255, 255, 0.055),
            rgba(0, 0, 0, 0.06) 55%,
            transparent 72%
        );
}


.nucleus-builder-particles {
    position: absolute;

    inset: 0;
}


.nucleus-builder-particle {
    position: absolute;

    transform:
        translate(-50%, -50%);

    border-radius: 50%;

    box-shadow:
        inset 2px 2px 3px rgba(255, 255, 255, 0.22),
        0 2px 5px rgba(0, 0, 0, 0.35);
}

.nucleus-builder-centre-label {
    position: absolute;

    left: 50%;
    top: 50%;

    transform:
        translate(-50%, -50%);

    z-index: 5;

    min-width: 0;

    padding: 0;

    border: 0;
    border-radius: 0;

    background: transparent;

    backdrop-filter: none;

    text-align: center;

    pointer-events: none;

    text-shadow:
        0 2px 5px rgba(0, 0, 0, 0.95),
        0 0 8px rgba(0, 0, 0, 0.85);
}

.nucleus-builder-notation {
    color: #fff;

    font-size: 33px;
    font-weight: 800;

    line-height: 1;
}


.nucleus-builder-notation sup,
.nucleus-builder-notation sub {
    color: #ffd39a;

    font-size: 12px;
}


.nucleus-builder-centre-label small {
    display: block;

    margin-top: 7px;

    color: var(--color-text-muted);

    font-size: 10px;
}


.nucleus-builder-legend {
    display: flex;

    justify-content: center;

    gap: 22px;
}


.nucleus-builder-legend span {
    display: flex;
    align-items: center;

    gap: 6px;

    color: var(--color-text-muted);

    font-size: 11px;
}


/* =========================================================
   STABILITY
   ========================================================= */

.nucleus-builder-stability {
    padding: 7px 11px;

    border-radius: 999px;

    font-size: 11px;
    font-weight: 800;
}


.nucleus-builder-stability.stable {
    border:
        1px solid rgba(82, 201, 123, 0.55);

    background:
        rgba(82, 201, 123, 0.12);

    color: #8de6aa;
}


.nucleus-builder-stability.unstable {
    border:
        1px solid rgba(232, 92, 82, 0.55);

    background:
        rgba(232, 92, 82, 0.12);

    color: #ff9c94;
}


.nucleus-builder-stability.neutral {
    border:
        1px solid rgba(255, 255, 255, 0.16);

    background:
        rgba(255, 255, 255, 0.055);

    color: var(--color-text-muted);
}


/* =========================================================
   ELEMENT RESULT
   ========================================================= */

.nucleus-builder-result {
    display: flex;
    flex-direction: column;
}


.nucleus-builder-element-tile {
    position: relative;

    min-height: 170px;

    margin-top: 14px;

    display: flex;
    flex-direction: column;

    align-items: center;
    justify-content: center;

    border:
        1px solid rgba(238, 172, 96, 0.42);

    border-radius: 13px;

    background:
        radial-gradient(
            circle,
            rgba(238, 172, 96, 0.14),
            transparent 70%
        );
}


.nucleus-builder-element-number {
    position: absolute;

    left: 10px;
    top: 8px;

    color: #ffd39a;

    font-size: 12px;
    font-weight: 700;
}


.nucleus-builder-element-symbol {
    color: #fff;

    font-size: 58px;
    line-height: 1;
}


.nucleus-builder-element-name {
    margin-top: 8px;

    color: var(--color-text-muted);

    font-size: 13px;
}


.nucleus-builder-result-data {
    display: grid;

    grid-template-columns:
        repeat(3, 1fr);

    gap: 6px;

    margin-top: 12px;
}


.nucleus-builder-result-data div {
    padding: 8px 4px;

    border-radius: 7px;

    background:
        rgba(255, 255, 255, 0.045);

    text-align: center;
}


.nucleus-builder-result-data span {
    display: block;

    color: var(--color-text-muted);

    font-size: 8px;
}


.nucleus-builder-result-data strong {
    display: block;

    margin-top: 3px;

    color: #fff;

    font-size: 16px;
}


.nucleus-builder-stability-text {
    margin-top: 13px;

    padding: 11px 12px;

    border-left:
        3px solid var(--color-accent);

    background:
        rgba(238, 172, 96, 0.055);

    color: var(--color-text-muted);

    font-size: 11px;
    line-height: 1.5;
}


/* =========================================================
   MINI PERIODIC TABLE
   ========================================================= */

.nucleus-builder-periodic-card {
    grid-column: 1 / -1;
}


.nucleus-builder-periodic-heading {
    display: flex;

    justify-content: space-between;
    align-items: flex-end;

    gap: 18px;

    margin-bottom: 16px;
}


.nucleus-builder-periodic-heading h3 {
    margin: 5px 0 0;

    color: #fff;

    font-size: 18px;
}


.nucleus-builder-periodic-heading p {
    max-width: 350px;

    margin: 0;

    color: var(--color-text-muted);

    font-size: 11px;
    line-height: 1.45;
}


.nucleus-builder-periodic-scroll {
    overflow-x: auto;

    padding-bottom: 6px;
}


.nucleus-builder-periodic-table {
    min-width: 760px;
}


.nucleus-builder-periodic-main {
    display: grid;

    grid-template-columns:
        repeat(
            18,
            minmax(32px, 1fr)
        );

    grid-auto-rows: 42px;

    gap: 4px;
}


/* =========================================================
   MINI PERIODIC TABLE CELLS
   ========================================================= */

.nucleus-builder-periodic-cell {
    position: relative;

    min-width: 0;
    height: 42px;

    display: flex;
    flex-direction: column;

    align-items: center;
    justify-content: center;

    padding: 3px;

    border:
        1px solid rgba(255, 255, 255, 0.12);

    border-radius: 7px;

    color: #fff;

    overflow: hidden;

    /*
     * Important:
     * don't inherit focus/highlight styling
     * from the actual periodic table.
     */
    outline: none;
    box-shadow: none;

    pointer-events: none;

    transition:
        transform 0.18s ease,
        outline-color 0.18s ease,
        box-shadow 0.18s ease;
}


.nucleus-builder-periodic-cell small {
    position: absolute;

    left: 5px;
    top: 4px;

    color:
        rgba(255, 255, 255, 0.82);

    font-size: 7px;
    font-weight: 700;
    line-height: 1;
}


.nucleus-builder-periodic-cell strong {
    margin: 4px 0 0;

    color: #fff;

    font-size: 13px;
    font-weight: 800;
    line-height: 1;
}


/*
 * Only the element produced by the nucleus
 * receives a highlight.
 */
.nucleus-builder-periodic-cell.nucleus-builder-current-element {
    outline:
        3px solid
        var(--color-accent);

    outline-offset: 1px;

    border-color:
        var(--color-accent);

    box-shadow:
        0 0 16px
        rgba(238, 172, 96, 0.65);

    transform:
        scale(1.12);

    z-index: 4;
}

.nucleus-builder-known-range {
    margin-top: 9px;
    padding: 8px 10px;

    border-radius: 8px;

    background:
        rgba(86, 134, 197, 0.09);

    color:
        var(--color-text-muted);

    font-size: 10px;
    line-height: 1.45;
}


.nucleus-builder-stepper button:disabled {
    opacity: 0.32;
    cursor: not-allowed;
}


.nucleus-builder-stepper button:disabled:hover {
    border-color:
        rgba(238, 172, 96, 0.32);

    background:
        rgba(8, 8, 8, 0.55);
}


/* =========================================================
   NUCLIDE DECAY + HISTORY
   ========================================================= */

.nucleus-builder-nuclide-info {
    grid-column: 1 / -1;

    display: grid;

    grid-template-columns:
        minmax(0, 1.25fr)
        minmax(280px, 0.75fr);

    gap: 20px;
}


.nucleus-builder-nuclide-section {
    min-width: 0;
}


.nucleus-builder-nuclide-section
+ .nucleus-builder-nuclide-section {

    padding-left: 20px;

    border-left:
        1px solid
        rgba(255, 255, 255, 0.08);
}


.nucleus-builder-nuclide-section h3 {
    margin: 6px 0 13px;

    color: #fff;

    font-size: 18px;
}


.nucleus-builder-decay-stats {
    display: grid;

    grid-template-columns:
        repeat(4, minmax(0, 1fr));

    gap: 8px;
}


.nucleus-builder-decay-stats div {
    min-width: 0;

    padding: 10px;

    border-radius: 8px;

    background:
        rgba(255, 255, 255, 0.045);
}


.nucleus-builder-decay-stats span {
    display: block;

    color:
        var(--color-text-muted);

    font-size: 9px;
}


.nucleus-builder-decay-stats strong {
    display: block;

    margin-top: 4px;

    color: #fff;

    font-size: 12px;
    line-height: 1.4;
}


.nucleus-builder-decay-equation {
    margin-top: 12px;
    padding: 12px 14px;

    border-left:
        3px solid
        var(--color-accent);

    background:
        rgba(238, 172, 96, 0.06);

    color: #ffd39a;

    font-size: 14px;
    font-weight: 700;
}


.nucleus-builder-nuclide-section > p {
    margin: 11px 0 0;

    color:
        var(--color-text-muted);

    font-size: 11px;
    line-height: 1.6;
}


.nucleus-builder-isotope-history-note {
    margin-top: 14px;
    padding: 11px 12px;

    border-radius: 9px;

    background:
        rgba(255, 255, 255, 0.035);
}


.nucleus-builder-isotope-history-note strong {
    color: #fff;

    font-size: 11px;
}


.nucleus-builder-isotope-history-note p {
    margin: 5px 0 0;

    color:
        var(--color-text-muted);

    font-size: 10px;
    line-height: 1.5;
}


.nucleus-builder-data-source {
    grid-column: 1 / -1;

    color:
        var(--color-text-muted);

    font-size: 9px;

    opacity: 0.75;
}


.nucleus-builder-stability.particle-unstable {
    border:
        1px solid
        rgba(238, 172, 96, 0.55);

    background:
        rgba(238, 172, 96, 0.12);

    color: #ffd39a;
}


@media (max-width: 760px) {

    /* =========================================
       MAIN PAGE
       ========================================= */

    .atom-builder-layout {
        padding: 10px 0 36px;
    }

    .atom-builder-header {
        align-items: flex-start;
        flex-direction: column;
        gap: 14px;
        margin-bottom: 16px;
    }

    .atom-builder-header h1 {
        font-size: clamp(2rem, 10vw, 2.8rem);
    }

    .atom-builder-header p {
        font-size: 0.92rem;
        line-height: 1.5;
    }


    /* =========================================
       MAIN BUILDER
       ========================================= */

    .atom-builder-grid {
        grid-template-columns: 1fr;
        gap: 14px;
    }

    /*
       display: contents lets the electron card
       become part of the main grid on mobile.
    */
    .atom-builder-right {
        display: contents;
    }

    .atom-builder-left {
        order: 1;
    }

    /*
       Put electron controls BEFORE the atom viewer.
    */
    .atom-builder-electron-card {
        order: 2;

        padding: 12px 14px;

        display: grid;
        grid-template-columns: auto 1fr;
        grid-template-areas:
            "label button"
            "electron button";

        align-items: center;
        gap: 6px 12px;
    }

    .atom-builder-workspace {
        order: 3;

        padding: 12px;
        border-radius: 16px;
    }

    .atom-builder-progress-card {
        order: 4;
    }


    /* =========================================
       MOBILE ELECTRON CONTROL
       ========================================= */

    .atom-builder-electron-card .atom-builder-small-label {
        grid-area: label;
    }

    .atom-builder-electron-card p,
    .atom-builder-electron-card small {
        display: none;
    }

    .atom-builder-electron-source {
        grid-area: electron;

        width: 52px;
        height: 52px;

        margin: 4px 0;

        font-size: 21px;
    }

    .atom-builder-accessible-add {
        grid-area: button;

        width: 100%;
        min-height: 50px;

        padding: 12px 16px;

        font-size: 15px;
        font-weight: 700;
    }


    /* =========================================
       WORKSPACE HEADER
       ========================================= */

    .atom-builder-workspace-header {
        gap: 10px;
        align-items: flex-start;
    }

    .atom-builder-workspace-header h2 {
        font-size: 1.25rem;
        line-height: 1.2;
        margin-top: 4px;
    }

    .atom-builder-shell-counter {
        flex-shrink: 0;
        padding: 6px 9px;
        font-size: 11px;
    }


    /* =========================================
       SMALLER ATOM GRAPHIC
       ========================================= */

    .atom-builder-stage {
        /*
         * IMPORTANT:
         * Do not use width: 100% here.
         */
        width: min(78vw, 300px);

        margin: 4px auto 8px;
    }

    .atom-builder-nucleus {
        width: 86px;
        height: 86px;
        gap: 3px;
    }

    .atom-builder-nucleus strong {
        font-size: 13px;
    }

    .atom-builder-placed-electron {
        width: 16px;
        height: 16px;
        font-size: 8px;
    }


    /* =========================================
       FEEDBACK UNDER ATOM
       ========================================= */

    .atom-builder-feedback {
        grid-template-columns: 1fr;

        margin-top: 8px;
    }

    .atom-builder-configuration-display {
        min-width: 0;

        padding: 12px 14px;

        border-right: 0;
        border-bottom:
            1px solid rgba(255, 177, 88, 0.18);
    }

    .atom-builder-configuration-value {
        font-size: 1.45rem;
    }

    .atom-builder-feedback .atom-builder-message {
        padding: 12px 14px;
        font-size: 0.9rem;
    }


    /* =========================================
       ELEMENT PICKER
       ========================================= */

    .atom-builder-picker-card,
    .atom-builder-selected-card,
    .atom-builder-progress-card {
        padding: 12px;
    }

    .atom-builder-element-choices {
        grid-template-columns:
            repeat(4, minmax(0, 1fr));

        gap: 6px;
    }

    .atom-builder-element-choice {
        min-height: 42px;
    }

    .atom-builder-element-tile {
        min-height: 145px;
    }

    .atom-builder-symbol {
        font-size: 48px;
    }


    /* =========================================
       ISOTOPE USE SECTION
       ========================================= */

    .atom-builder-isotope-use-grid {
        grid-template-columns: 1fr;
    }

    .atom-builder-isotope-concept {
        grid-template-columns: 1fr;
    }

    .atom-builder-isotope-concept-symbol {
        border-right: 0;

        border-bottom:
            1px solid rgba(238, 172, 96, 0.22);
    }


    /* =========================================
       NUCLEUS BUILDER
       ========================================= */

    .nucleus-builder-header {
        align-items: flex-start;
        flex-direction: column;
        gap: 12px;
    }

    .nucleus-builder-grid {
        grid-template-columns: 1fr;
        gap: 14px;
    }

    .nucleus-builder-card {
        padding: 14px;
    }

    .nucleus-builder-result {
        grid-column: auto;
        display: flex;
    }

    .nucleus-builder-stage {
        width: min(76vw, 280px);
    }

    .nucleus-builder-periodic-heading {
        align-items: flex-start;
        flex-direction: column;
    }

}