:root {

    /* MOTION SYSTEM */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-soft: cubic-bezier(0.22, 1, 0.36, 1);

    --fast: 120ms;
    --normal: 220ms;

    /* BRAND */
    --accent: #3b82f6;
}

/* GLOBAL */

html,
body {
    height: 100%;
}

body {
    margin: 0;
    font-family: "Inter", system-ui, sans-serif;

    min-height: 100vh;

    background: radial-gradient(circle at top, #1a1a1a, #0f0f0f);
    color: #e5e5e5;
}

body.light {
    background: linear-gradient(135deg, #f8fafc, #e2e8f0);
    color: #0f172a;
}

/* APP LAYOUT */

.app {
    max-width: 900px;
    margin: 100px auto;
    padding: 0 20px;

    display: grid;
    grid-template-columns: 1fr 1.2fr;
    gap: 40px;

    animation: enter 0.6s var(--ease-out);
}

@keyframes enter {
    from {
        opacity: 0;
        transform: translateY(14px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* PANEL */

.panel {
    padding: 30px;
    border-radius: 20px;

    background: rgba(30, 30, 30, 0.75);
    border: 1px solid rgba(255, 255, 255, 0.08);

    backdrop-filter: blur(14px);

    transition:
        transform var(--normal) var(--ease-soft),
        box-shadow var(--normal) var(--ease-soft),
        border-color var(--normal) var(--ease-soft);
}

body.light .panel {
    background: rgba(255, 255, 255, 0.9);
    border: 1px solid #d0d7de;
}

/* HERO */

.hero {
    text-align: center;
    margin-bottom: 20px;
}

.hero h1 {
    margin: 0;
    font-size: 28px;
    letter-spacing: -0.03em;
}

.hero p {
    font-size: 13px;
    opacity: 0.6;
    margin-top: 6px;
}

/* INPUT */

.input-wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 12px;

    margin-bottom: 20px;
}

.input-wrapper input {
    width: 70%;
    text-align: center;

    font-size: 52px;
    font-weight: 700;

    padding: 10px;
    border-radius: 12px;

    background: rgba(255, 255, 255, 0.06);
    border: 1px solid rgba(255, 255, 255, 0.1);

    color: inherit;

    transition:
        transform var(--normal) var(--ease-out),
        box-shadow var(--normal) var(--ease-out),
        border-color var(--normal) var(--ease-out);
}

.input-wrapper input:focus {
    outline: none;

    border-color: rgba(59, 130, 246, 0.8);

    box-shadow:
        0 0 0 4px rgba(59, 130, 246, 0.12),
        0 12px 30px rgba(0, 0, 0, 0.25);

    transform: translateY(-1px);
}

body.light .input-wrapper input {
    background: white;
    border: 2px solid #94a3b8;
}

/* STEP BUTTONS */

.step-btn {
    width: 42px;
    height: 42px;

    border-radius: 12px;

    border: 1px solid rgba(255, 255, 255, 0.08);
    background: rgba(255, 255, 255, 0.06);

    color: inherit;
    font-size: 20px;

    cursor: pointer;

    transition:
        transform 120ms cubic-bezier(0.22, 1, 0.36, 1),
        box-shadow 220ms ease,
        border-color 220ms ease;
}

.step-btn:hover {
    transform: scale(1.08);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

.step-btn:active {
    transform: scale(0.92);
}

body.light .step-btn {
    background: white;
    border: 1px solid #cbd5e1;
    color: #0f172a;
}

/* CONTROLS */

.controls {
    display: flex;
    gap: 10px;
}

/* CUSTOM SELECT */

.custom-select {
    position: relative;
    flex: 1;
}

.select-trigger {
    padding: 10px;
    border-radius: 10px;

    background: rgba(35, 35, 35, 0.9);
    border: 1px solid rgba(255, 255, 255, 0.08);

    cursor: pointer;

    transition: background 220ms var(--ease-out);
}

.select-options {
    position: absolute;
    width: 100%;
    margin-top: 8px;

    border-radius: 12px;

    background: rgba(35, 35, 35, 0.95);
    border: 1px solid rgba(255, 255, 255, 0.08);

    opacity: 0;
    transform: translateY(-10px) scale(0.98);
    pointer-events: none;

    transition: all 0.28s var(--ease-out);
}

.custom-select.open .select-options {
    opacity: 1;
    transform: translateY(0) scale(1);
    pointer-events: auto;
}

.option {
    padding: 10px;
    cursor: pointer;
}

.option:hover {
    background: rgba(60, 60, 60, 0.6);
}

.option.active {
    color: var(--accent);
    font-weight: 600;
}

.option.active::before {
    content: "•";
    margin-right: 6px;
    color: var(--accent);
}

body.light .select-trigger {
    background: white;
    border: 1px solid #cbd5e1;
    color: #0f172a;
}

body.light .select-options {
    background: white;
    border: 1px solid #cbd5e1;
}

body.light .option:hover {
    background: #f1f5f9;
}

/* SWAP BUTTON */

#swap-btn {
    padding: 10px 12px;
    border-radius: 10px;

    border: 1px solid rgba(255, 255, 255, 0.1);
    background: rgba(255, 255, 255, 0.06);

    color: inherit;
    cursor: pointer;

    transition:
        transform 120ms cubic-bezier(0.22, 1, 0.36, 1),
        border-color 220ms ease,
        background 220ms ease;
}

#swap-btn:hover {
    transform: rotate(180deg) scale(1.05);
    border-color: rgba(59, 130, 246, 0.4);
}

body.light #swap-btn {
    background: white;
    border: 1px solid #cbd5e1;
    color: #0f172a;
}

/* RESULT PANEL */

.result-panel {
    display: grid;
    gap: 16px;
}

/* CARD */
.card {
    padding: 18px;
    border-radius: 14px;

    background: rgba(35, 35, 35, 0.7);
    border: 1px solid rgba(255, 255, 255, 0.08);

    cursor: pointer;

    animation: fadeUp 0.35s var(--ease-out);

    transition:
        transform var(--normal) var(--ease-out),
        box-shadow var(--normal) var(--ease-out),
        border-color var(--normal) var(--ease-out);
}

@keyframes fadeUp {
    from {
        opacity: 0;
        transform: translateY(6px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.card:hover {
    transform: translateY(-6px) scale(1.015);
    box-shadow: 0 18px 40px rgba(0, 0, 0, 0.35);
    border-color: rgba(59, 130, 246, 0.35);
}

body.light .card {
    background: white;
    border: 1px solid #cbd5e1;
}

/* CARD HEADER */
.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
}

/* COPY BUTTON */
.copy-btn {
    background: transparent;
    border: none;
    cursor: pointer;

    font-size: 14px;
    opacity: 0.6;

    transition: transform 150ms ease, opacity 150ms ease;
}

.copy-btn:hover {
    transform: scale(1.15);
    opacity: 1;
}

/* LABEL */
.label-pill {
    font-size: 11px;
    padding: 4px 10px;
    border-radius: 999px;

    background: rgba(255, 255, 255, 0.06);
    border: 1px solid rgba(255, 255, 255, 0.08);

    text-transform: uppercase;
    letter-spacing: 0.05em;
}

body.light .label-pill {
    background: #f1f5f9;
    border: 1px solid #cbd5e1;
}

/* THEME BUTTON */

.theme-btn {
    position: fixed;
    top: 20px;
    right: 20px;

    padding: 8px 12px;
    border-radius: 10px;

    border: 1px solid rgba(255, 255, 255, 0.12);
    background: rgba(255, 255, 255, 0.06);

    cursor: pointer;
}

body.light .theme-btn {
    background: white;
    border: 1px solid #cbd5e1;
}

/* TOAST */
.copy-toast {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);

    background: rgba(0, 0, 0, 0.75);
    color: white;

    padding: 10px 14px;
    border-radius: 10px;

    font-size: 13px;

    opacity: 0;
    pointer-events: none;

    transition: opacity 200ms ease, transform 200ms ease;
}

.copy-toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(-6px);
}

/* MOBILE */

@media (max-width: 700px) {
    .app {
        grid-template-columns: 1fr;
    }

    .input-wrapper input {
        width: 100%;
        font-size: 44px;
    }
}

/* INPUT FIX */

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type="number"] {
    -moz-appearance: textfield;
}