.pulse-calculator {
    font-family: var(--font-body);
    max-width: 28rem;
    margin: 0 auto;
    width: 100%;
    padding: 1rem;
    box-sizing: border-box;
}

.pulse-calculator * {
    box-sizing: border-box;
}

.navigation {
    margin-bottom: 1.25rem;
}

.nav-steps {
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 0.75rem;
}

.nav-step {
    width: 1.5rem;
    height: 1.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    background: var(--line-1);
    color: var(--text-secondary-6);
}

.nav-step.active {
    background: var(--navy);
    color: white;
    transform: scale(1.05);
}

.nav-step:hover {
    background: var(--line-3);
}

.nav-step.active:hover {
    background: var(--navy);
}

.nav-line {
    width: 2rem;
    height: 0.125rem;
    margin: 0 0.25rem;
    background: var(--line-1);
    transition: all 0.2s;
}

.nav-line.active {
    background: var(--navy);
}

.nav-labels {
    display: flex;
    justify-content: center;
    gap: 1rem;
    font-size: 0.75rem;
}

.nav-label {
    padding: 0.25rem 0.5rem;
    border-radius: 0.25rem;
    cursor: pointer;
    transition: all 0.2s;
    background: none;
    border: none;
    color: var(--text-secondary-6);
}

.nav-label.active {
    color: var(--navy);
    font-weight: 500;
}

.nav-label:hover {
    color: var(--navy);
    background: var(--bg);
}

.page-title {
    text-align: center;
    margin-bottom: 2rem;
    font-size: 2rem;
    font-weight: bold;
    color: var(--navy);
    line-height: 1.2;
}

.section {
    background: white;
    border-radius: var(--radius-xxl);
    box-shadow: var(--shadow-card);
    border: 1px solid var(--line-1);
    padding: 1rem;
    margin-bottom: 1rem;
}

.section-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--navy);
}

.section-number {
    width: 1.25rem;
    height: 1.25rem;
    background: var(--red);
    color: white;
    font-family: var(--font-mono);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
}

.input-field {
    padding: 0.75rem;
    border: 1px solid var(--line-3);
    border-radius: var(--radius-m);
    background: var(--field-bg);
    text-align: center;
    font-size: 0.875rem;
    font-weight: 500;
    transition: all 0.2s;
    width: 100%;
    box-sizing: border-box;
}

.input-field:focus {
    outline: none;
    border-color: var(--red);
    box-shadow: 0 0 0 1px var(--red);
}

.input-field:hover {
    background: var(--field-bg);
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
    margin-bottom: 0.75rem;
}

.input-label {
    font-size: 0.75rem;
    color: var(--text-secondary-6);
    font-weight: 500;
}

.method-toggle {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.method-btn {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--line-3);
    border-radius: 0.5rem;
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    background: var(--field-bg);
    color: var(--text-secondary-8);
    flex: 1;
    min-width: 0;
    overflow-wrap: anywhere;
    text-align: center;
}

.method-btn.active {
    background: var(--navy);
    color: white;
    border-color: var(--navy);
}

.method-btn:hover {
    background: var(--line-1);
}

.method-btn.active:hover {
    background: var(--navy);
}

.unit-toggle {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.unit-btn {
    padding: 0.5rem 1rem;
    border: 1px solid var(--line-3);
    border-radius: var(--radius-pill);
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    background: var(--field-bg);
    color: var(--text-secondary-8);
    flex: 1;
}

.unit-btn.active {
    background: var(--navy);
    color: white;
    border-color: var(--navy);
}

.unit-btn:hover {
    background: var(--line-1);
}

.unit-btn.active:hover {
    background: var(--navy);
}

.gender-toggle {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.gender-btn {
    padding: 0.5rem 1rem;
    border: 1px solid var(--line-3);
    border-radius: 0.5rem;
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    background: var(--field-bg);
    color: var(--text-secondary-8);
    flex: 1;
}

.gender-btn.active {
    background: var(--navy);
    color: white;
    border-color: var(--navy);
}

.gender-btn:hover {
    background: var(--line-1);
}

.gender-btn.active:hover {
    background: var(--navy);
}

.result-main {
    background: var(--navy);
    border-radius: var(--radius-l);
    padding: 1rem;
    color: white;
    margin-bottom: 1rem;
    text-align: center;
}

.result-header {
    display: flex;
    align-items: center;
    justify-content: flex-start;
    gap: 0.5rem;
    margin-bottom: 0.25rem;
}

.result-title {
    font-size: 0.75rem;
    font-weight: 600;
    opacity: 0.9;
}

.result-value {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    font-weight: 500;
    margin-bottom: 0.25rem;
}

.result-subtitle {
    color: var(--line-3);
    font-size: 0.75rem;
}

.zone-results {
    display: grid;
    gap: 0.5rem;
    margin-top: 0.75rem;
}

.zone-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 0.5rem;
    font-size: 0.875rem;
    color: white;
}

.zone-item-name {
    flex: 1;
    font-weight: 500;
    text-align: left;
}

.zone-item-range {
    font-weight: 600;
    color: var(--line-3);
}

.zones-section {
    margin-top: 1rem;
}

.zones-category {
    margin-bottom: 1.5rem;
}

.zones-category h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--navy);
    margin-bottom: 0.5rem;
    padding-bottom: 0.25rem;
    border-bottom: 2px solid var(--navy);
}

.zones-list {
    display: grid;
    gap: 0.25rem;
}

.zone-detail {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    background: var(--field-bg);
    border-radius: 0.5rem;
    font-size: 0.875rem;
    border-left: 4px solid transparent;
}

.zone-detail.health { border-left-color: #10b981; }
.zone-detail.fat-burn { border-left-color: #f59e0b; }
.zone-detail.aerobic { border-left-color: #ef4444; }
.zone-detail.anaerobic { border-left-color: #8b5cf6; }
.zone-detail.max { border-left-color: #ec4899; }

.zone-detail-info {
    flex: 1;
    text-align: left;
}

.zone-detail-name {
    font-weight: 600;
    color: var(--navy);
    margin-bottom: 0.125rem;
}

.zone-detail-desc {
    font-size: 0.75rem;
    color: var(--text-secondary-6);
}

.zone-detail-range {
    font-weight: 600;
    color: var(--text-secondary-8);
    text-align: right;
}

/* Mobile First Responsive Design */
@media (max-width: 480px) {
    .page-title {
        font-size: 1.5rem;
        margin-bottom: 1.5rem;
    }

    .pulse-calculator {
        padding: 0.5rem;
    }

    .section {
        padding: 0.75rem;
    }

    .input-field {
        padding: 0.5rem;
    }
}

@media (min-width: 640px) {
    .pulse-calculator {
        max-width: 85vw;
        width: 85%;
    }
}

@media (min-width: 768px) {
    .pulse-calculator {
        max-width: 75vw;
        width: 75%;
    }
}

@media (min-width: 1024px) {
    .pulse-calculator {
        max-width: 65vw;
        width: 65%;
    }
}

@media (min-width: 1280px) {
    .pulse-calculator {
        max-width: 55vw;
        width: 55%;
    }
}