:root {
  --eq-ink: #28344b;
  --eq-muted: #59687d;
  --eq-border: #c9d3e1;
  --eq-panel: #f7f9fc;
  --eq-accent: #3d5ca8;
  --eq-accent-dark: #29427e;
  --eq-soft: #eaf0ff;
  --eq-warm: #fff6df;
}
* { box-sizing: border-box; }
body { color: var(--eq-ink); }
.calculator-panel, .result-panel { background: var(--eq-panel); border: 1px solid var(--eq-border); border-radius: 14px; padding: clamp(18px, 3vw, 30px); margin-block: 1rem; }
.calculator-panel h2, .result-panel h2 { margin-top: 0; }
fieldset { border: 1px solid var(--eq-border); border-radius: 12px; margin: 1.1rem 0; padding: 1rem; background: #fff; min-width: 0; }
legend { font-weight: 800; padding-inline: .4rem; }
.field-group { margin-block: 1rem; }
.field-group.compact { margin-block: .65rem; }
.field-group label { display: block; font-weight: 700; margin-bottom: .4rem; }
input, select, button { font: inherit; }
input, select { width: 100%; min-height: 44px; border: 1px solid #9aaec8; border-radius: 9px; padding: .55rem .7rem; color: var(--eq-ink); background: #fff; }
input:focus-visible, select:focus-visible, button:focus-visible, a:focus-visible { outline: 3px solid #e3aa29; outline-offset: 2px; }
input[aria-invalid="true"], select[aria-invalid="true"] { border-color: #ad3a35; box-shadow: 0 0 0 2px #f6d8d5; }
.help-text { color: var(--eq-muted); font-size: .92rem; margin: .35rem 0 0; }
.input-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.four-columns { grid-template-columns: repeat(4, minmax(0, 1fr)); gap: .75rem; }
.narrow-field { max-width: 30rem; }
.actions { display: flex; flex-wrap: wrap; gap: .65rem; margin-top: 1.25rem; }
.button { border: 1px solid #91a8c8; border-radius: 999px; background: #fff; color: var(--eq-accent-dark); padding: .62rem 1rem; cursor: pointer; min-height: 42px; }
.button:hover:not(:disabled) { background: var(--eq-soft); }
.button:disabled { cursor: not-allowed; opacity: .52; }
.button-primary { background: var(--eq-accent); border-color: var(--eq-accent); color: #fff; }
.button-primary:hover:not(:disabled) { background: var(--eq-accent-dark); }
.form-error { color: #9b2d29; min-height: 1.5em; margin: 1rem 0 0; }
.section-heading { display: flex; justify-content: space-between; align-items: baseline; gap: 1rem; flex-wrap: wrap; }
.status { color: var(--eq-muted); margin: 0; }
.result-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: .75rem; margin-block: 1.2rem; }
.metric { border: 1px solid var(--eq-border); background: #fff; border-radius: 10px; padding: .75rem; min-width: 0; }
.metric-label { display: block; color: var(--eq-muted); font-size: .9rem; margin-bottom: .25rem; }
.metric strong { display: block; overflow-wrap: anywhere; font-size: clamp(1rem, 2vw, 1.2rem); }
.steps { border-left: 4px solid var(--eq-accent); background: var(--eq-soft); border-radius: 4px; padding: .8rem 1rem; min-height: 3rem; line-height: 1.7; }
.steps p { margin: 0; }
.reaction-diagram { display: grid; grid-template-columns: minmax(0, 1fr) minmax(80px, .32fr) minmax(0, 1fr); align-items: center; gap: .75rem; margin-top: 1.2rem; padding: 1rem; border: 1px solid var(--eq-border); border-radius: 12px; background: linear-gradient(135deg, #fbfcff, #eef3ff); }
.species-card { min-width: 0; padding: 1rem .65rem; border: 1px solid #b8c7e5; border-radius: 10px; background: #fff; text-align: center; }
.species-label { display: block; font-weight: 800; font-size: clamp(1rem, 2.5vw, 1.45rem); overflow-wrap: anywhere; }
.species-note { display: block; color: var(--eq-muted); margin-top: .35rem; font-size: .9rem; }
.equilibrium-arrow { color: var(--eq-accent); text-align: center; font-size: clamp(2rem, 5vw, 3rem); line-height: 1; }
.diagram-note { color: var(--eq-muted); font-size: .92rem; margin: .75rem 0; }
.details { margin-top: 1.35rem; }
.details h3 { margin-bottom: .6rem; }
@media (max-width: 720px) {
  .four-columns { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .result-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 430px) {
  .calculator-panel, .result-panel { padding: 16px; }
  .input-grid, .four-columns { grid-template-columns: 1fr; gap: .25rem; }
  .actions { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .button { width: 100%; padding-inline: .55rem; }
  .reaction-diagram { grid-template-columns: 1fr; gap: .45rem; }
  .equilibrium-arrow { transform: rotate(90deg); }
}