/* Mode tabs */
.tab-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.5rem 1rem;
    border: 2px solid var(--border, #e2e8f0);
    border-radius: 8px;
    background: var(--surface, #fff);
    color: var(--text-secondary, #64748b);
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    transition: all .2s;
}

.tab-btn:hover {
    border-color: var(--primary, #6366f1);
    color: var(--primary, #6366f1);
}

.tab-btn.tab-active {
    background: var(--primary, #6366f1);
    border-color: var(--primary, #6366f1);
    color: #fff;
}

/* Power sub-tabs */
.mode-hint {
    font-size: 0.85rem;
    color: var(--text-secondary, #64748b);
    margin-bottom: 0.6rem;
}

.sub-tabs {
    display: flex;
    gap: 0.4rem;
    margin-bottom: 1rem;
}

.sub-tab {
    padding: 0.3rem 0.8rem;
    border: 1.5px solid var(--border, #e2e8f0);
    border-radius: 6px;
    background: var(--surface, #fff);
    font-size: 0.82rem;
    font-weight: 600;
    cursor: pointer;
    color: var(--text-secondary, #64748b);
    transition: all .15s;
}

.sub-tab:hover,
.sub-tab.sub-tab-active {
    background: var(--primary, #6366f1);
    border-color: var(--primary, #6366f1);
    color: #fff;
}

/* Visual formula */
.formula-display {
    text-align: center;
    margin: 1rem 0 1.5rem;
    padding: 1rem;
    background: var(--surface-alt, #f8fafc);
    border-radius: 12px;
    border: 1px solid var(--border, #e2e8f0);
}

.formula-box {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 1.8rem;
    font-family: 'Georgia', serif;
    font-weight: 700;
    color: var(--primary, #ffffff);
}

.formula-eq {
    color: var(--text, #ffffff);
    font-weight: 400;
}

.formula-fraction {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    line-height: 1.1;
}

.formula-num {
    font-size: 1.4rem;
    color: var(--text, #ffffff);
    font-weight: 700;
    border-bottom: 2px solid var(--text, #ffffff);
    padding: 0 0.3rem 2px;
}

.formula-den {
    font-size: 1.4rem;
    color: var(--text, #ffffff);
    font-weight: 700;
}

.formula-highlight {
    color: var(--primary, #ffffff);
}

.formula-caption {
    margin-top: 0.4rem;
    font-size: 0.82rem;
    color: var(--text-secondary, #64748b);
}

/* Inputs */
.input-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1.25rem;
}

@media (max-width: 500px) {
    .input-row {
        grid-template-columns: 1fr;
    }
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.input-group label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary, #64748b);
}

.input-with-unit {
    display: flex;
    border: 2px solid var(--border, #e2e8f0);
    border-radius: 8px;
    overflow: hidden;
    transition: border-color .2s;
}

.input-with-unit:focus-within {
    border-color: var(--primary, #6366f1);
}

.input-with-unit input {
    flex: 1;
    border: none;
    outline: none;
    padding: 0.55rem 0.75rem;
    font-size: 1rem;
    background: var(--surface, #fff);
    color: var(--text, #1e293b);
    min-width: 0;
}

.input-with-unit select {
    border: none;
    border-left: 2px solid var(--border, #e2e8f0);
    outline: none;
    padding: 0.55rem 0.5rem;
    font-size: 0.82rem;
    font-weight: 600;
    background: var(--surface-alt, #f8fafc);
    color: var(--text-secondary, #64748b);
    cursor: pointer;
}

/* Button */
.btn-calc {
    width: 100%;
    padding: 0.85rem;
    background: var(--primary, #6366f1);
    color: #fff;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 700;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: background .2s, transform .1s;
    margin-top: 0.25rem;
}

.btn-calc:hover {
    background: var(--primary-dark, #4f46e5);
}

.btn-calc:active {
    transform: scale(.98);
}

/* Result */
.result-box {
    margin: 1.25rem 0;
    padding: 1.25rem 1.5rem;
    background: linear-gradient(135deg, var(--primary, #6366f1) 0%, var(--primary-dark, #4f46e5) 100%);
    border-radius: 14px;
    color: #fff;
}

.result-main {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
    margin-bottom: 0.75rem;
}

.result-label {
    font-size: 0.82rem;
    font-weight: 600;
    opacity: 0.8;
    text-transform: uppercase;
    letter-spacing: .05em;
}

.result-value {
    font-size: 2rem;
    font-weight: 700;
}

.result-conversions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 0.5rem;
}

.conv-chip {
    background: rgba(255, 255, 255, 0.18);
    border-radius: 6px;
    padding: 0.25rem 0.65rem;
    font-size: 0.83rem;
    font-weight: 600;
}

.result-sub-values {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 0.5rem;
}

.sub-chip {
    background: rgba(255, 255, 255, 0.12);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 6px;
    padding: 0.3rem 0.75rem;
    font-size: 0.82rem;
    font-weight: 600;
}

.result-formula-used {
    font-size: 0.82rem;
    opacity: 0.75;
    border-top: 1px solid rgba(255, 255, 255, 0.25);
    padding-top: 0.6rem;
    margin-top: 0.25rem;
}

/* Error */
.calc-error {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    padding: 0.85rem 1rem;
    background: #fef2f2;
    border: 1px solid #fecaca;
    border-radius: 10px;
    color: #b91c1c;
    font-size: 0.9rem;
    font-weight: 600;
    margin: 1rem 0;
}

/* Ohm triangle */
.ohm-triangle-section {
    margin: 2rem 0 1.5rem;
}

.ohm-triangle-section h2 {
    font-size: 1.1rem;
    margin-bottom: 0.35rem;
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.ohm-triangle-section>p {
    font-size: 0.85rem;
    color: var(--text-secondary, #64748b);
    margin-bottom: 1rem;
}

.triangle-wrap {
    display: flex;
    align-items: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.triangle-wrap svg {
    width: 220px;
    flex-shrink: 0;
}

.triangle-formulas {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

.tri-formula {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text, #1e293b);
    font-family: 'Georgia', serif;
}

.tri-var {
    display: inline-block;
    width: 1.5rem;
    color: var(--primary, #6366f1);
    font-size: 1.15rem;
}

.tri-formula.tri-power {
    color: var(--text-secondary, #64748b);
    font-size: 0.9rem;
    margin-top: 0.4rem;
}

.tri-var-power {
    color: #f59e0b;
}

/* Reference Table */
.ref-table-section {
    margin: 2rem 0 1.5rem;
}

.ref-table-section h2 {
    font-size: 1.1rem;
    margin-bottom: 0.35rem;
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.ref-table-section>p {
    font-size: 0.85rem;
    color: var(--text-secondary, #64748b);
    margin-bottom: 0.9rem;
}

.ref-table-wrap {
    overflow-x: auto;
    border-radius: 10px;
    border: 1px solid var(--border, #e2e8f0);
}

.ref-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.86rem;
}

.ref-table thead tr {
    background: var(--surface-alt, #f8fafc);
}

.ref-table th {
    padding: 0.65rem 1rem;
    text-align: left;
    font-weight: 700;
    color: var(--text-secondary, #64748b);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: .04em;
    border-bottom: 2px solid var(--border, #e2e8f0);
    white-space: nowrap;
}

.ref-table td {
    padding: 0.6rem 1rem;
    border-bottom: 1px solid var(--border, #e2e8f0);
    color: var(--text, #1e293b);
    white-space: nowrap;
}

.ref-table tbody tr:last-child td {
    border-bottom: none;
}

.ref-table tbody tr:hover {
    background: var(--surface-alt, #f8fafc);
}

/* Text formula */
.formula-text-block {
    background: var(--surface-alt, #f8fafc);
    border-left: 4px solid var(--primary, #6366f1);
    border-radius: 6px;
    padding: 0.75rem 1rem;
    margin: 0.75rem 0;
    font-family: 'Courier New', monospace;
    font-size: 1rem;
    color: var(--text, #1e293b);
}