:root {
    --bg-top: #efe5d5;
    --bg-bottom: #d6e1ea;
    --card: rgba(255, 250, 243, 0.84);
    --line: rgba(39, 45, 52, 0.12);
    --text: #182027;
    --muted: #55606d;
    --internal: #9d3c27;
    --external: #1d5f74;
    --accent: #d08b33;
    --shadow: 0 20px 60px rgba(24, 32, 39, 0.12);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    font-family: "Trebuchet MS", "Segoe UI", sans-serif;
    color: var(--text);
    background:
        radial-gradient(circle at top left, rgba(208, 139, 51, 0.18), transparent 28%),
        radial-gradient(circle at bottom right, rgba(29, 95, 116, 0.2), transparent 24%),
        linear-gradient(180deg, var(--bg-top), var(--bg-bottom));
}

.shell {
    width: min(1180px, calc(100% - 2rem));
    margin: 0 auto;
    padding: 2rem 0 3rem;
}

.card {
    background: var(--card);
    border: 1px solid rgba(255, 255, 255, 0.45);
    border-radius: 24px;
    box-shadow: var(--shadow);
    backdrop-filter: blur(18px);
}

.hero {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 1.5rem;
    padding: 2rem;
    margin-bottom: 1.5rem;
}

.eyebrow {
    margin: 0 0 0.5rem;
    font-size: 0.8rem;
    font-weight: 700;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--internal);
}

h1,
h2,
h3,
p {
    margin-top: 0;
}

h1 {
    margin-bottom: 0.75rem;
    font-size: clamp(2rem, 5vw, 3.5rem);
    line-height: 0.95;
}

.lede,
.hero-note p,
.notes-panel li,
.formula-block p,
.result-row span,
label span {
    color: var(--muted);
}

.hero-note {
    padding: 1.25rem;
    border-radius: 20px;
    background: linear-gradient(135deg, rgba(255, 255, 255, 0.72), rgba(255, 241, 220, 0.88));
    align-self: end;
}

.grid {
    display: grid;
    grid-template-columns: minmax(320px, 1.15fr) minmax(320px, 1fr);
    gap: 1.5rem;
    align-items: start;
}

.form-panel,
.result-panel,
.notes-panel {
    padding: 1.5rem;
}

.results-column {
    display: grid;
    gap: 1.5rem;
}

.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    margin-bottom: 1rem;
}

button,
input,
select {
    font: inherit;
}

button {
    border: 0;
    border-radius: 999px;
    padding: 0.8rem 1.2rem;
    font-weight: 700;
    color: #fffdf8;
    background: linear-gradient(135deg, #1d5f74, #9d3c27);
    cursor: pointer;
}

.field-grid {
    display: grid;
    gap: 1rem;
}

label {
    display: grid;
    gap: 0.45rem;
}

input,
select,
.suffix {
    width: 100%;
    border: 1px solid var(--line);
    border-radius: 16px;
    padding: 0.85rem 1rem;
    background: rgba(255, 255, 255, 0.75);
    color: var(--text);
}

.input-group,
.compound-group {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 0.65rem;
}

.compound-group select {
    min-width: 110px;
}

.suffix {
    display: grid;
    place-items: center;
    min-width: 72px;
}

.formula-block {
    margin-top: 1.5rem;
    padding-top: 1.25rem;
    border-top: 1px solid var(--line);
}

.error-box {
    margin-bottom: 1rem;
    padding: 1rem 1.1rem;
    border-radius: 18px;
    background: rgba(157, 60, 39, 0.1);
    border: 1px solid rgba(157, 60, 39, 0.18);
}

.error-box ul,
.notes-panel ul {
    margin: 0.75rem 0 0;
    padding-left: 1.2rem;
}

.result-panel {
    position: relative;
    overflow: hidden;
}

.result-panel::before {
    content: "";
    position: absolute;
    inset: 0 0 auto;
    height: 5px;
}

.accent-internal::before {
    background: linear-gradient(90deg, var(--internal), rgba(157, 60, 39, 0.18));
}

.accent-external::before {
    background: linear-gradient(90deg, var(--external), rgba(29, 95, 116, 0.18));
}

.pill {
    border-radius: 999px;
    padding: 0.4rem 0.8rem;
    font-size: 0.84rem;
    color: var(--muted);
    background: rgba(255, 255, 255, 0.78);
}

.result-row {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.9rem 0;
    border-bottom: 1px solid var(--line);
}

.result-row:last-child {
    border-bottom: 0;
}

.result-row strong {
    text-align: right;
}

@media (max-width: 920px) {
    .hero,
    .grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .shell {
        width: min(100% - 1rem, 100%);
        padding-top: 1rem;
    }

    .card {
        border-radius: 20px;
    }

    .hero,
    .form-panel,
    .result-panel,
    .notes-panel {
        padding: 1.2rem;
    }

    .input-group,
    .compound-group,
    .result-row,
    .panel-header {
        grid-template-columns: 1fr;
        display: grid;
    }

    .result-row strong {
        text-align: left;
    }
}