@font-face {
    font-family: 'Inter';
    src: url('../../assets/fonts/Inter.ttf') format('truetype');
    font-weight: 100 900;
    font-display: swap;
}

:root {
    --primary: #0f172a;
    --primary-light: #1e293b;
    --secondary: #1e3a5f;
    --accent: #3b82f6;
    --accent-light: #eff6ff;
    --bg: #f1f5f9;
    --surface: #ffffff;
    --text: #0f172a;
    --text-secondary: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-lg: 0 10px 25px rgba(0,0,0,0.08);
    --radius: 16px;
    --radius-sm: 10px;
    --font: 'Inter', -apple-system, sans-serif;
}

body.dark-theme {
    --bg: #0a1929;
    --surface: #112233;
    --text: #e9ecef;
    --text-secondary: #8696a7;
    --border: #334b61;
    --shadow: 0 1px 3px rgba(0,0,0,0.4);
    --primary: #3b82f6;
    --accent-light: #1e3a5f;
}

* { margin: 0; padding: 0; box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    -webkit-font-smoothing: antialiased;
    -webkit-user-select: none;
    user-select: none;
    min-height: 100dvh;
    transition: background-color 0.3s, color 0.3s;
}

.app-container {
    max-width: 480px;
    margin: 0 auto;
    background: var(--bg);
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
}

.app-header {
    background: linear-gradient(145deg, #0f172a 0%, #1e3a5f 50%, #1a365d 100%);
    color: white;
    padding: 1.25rem 1.5rem;
    position: sticky;
    top: 0;
    z-index: 10;
    box-shadow: 0 2px 8px rgba(0,0,0,0.12);
}

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

.theme-switcher {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    flex-shrink: 0;
    color: rgba(255,255,255,0.8);
    font-size: 0.85rem;
}

.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: rgba(255,255,255,0.25);
    transition: 0.3s;
    border-radius: 24px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 18px;
    width: 18px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: 0.3s;
    border-radius: 50%;
}

input:checked + .slider {
    background-color: var(--accent);
}

input:checked + .slider:before {
    transform: translateX(20px);
}

.app-header h1 {
    font-size: 1.25rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.app-header p {
    font-size: .8rem;
    opacity: .65;
    margin-top: .15rem;
    font-weight: 400;
}

.main-content {
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    flex: 1;
}

.card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1.25rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
}

.card-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 1rem;
    padding-bottom: .5rem;
    border-bottom: 2px solid var(--border);
}

.form-group {
    margin-bottom: .85rem;
}

.form-group label {
    display: block;
    font-size: .75rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: .3rem;
    text-transform: uppercase;
    letter-spacing: .04em;
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: .7rem .85rem;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: .9rem;
    font-family: var(--font);
    background: var(--surface);
    color: var(--text);
    transition: border-color .2s, box-shadow .2s;
    -webkit-appearance: none;
    appearance: none;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59,130,246,0.1);
}

.form-group .input-unit {
    display: flex;
    align-items: center;
    gap: .5rem;
}

.form-group .input-unit input {
    flex: 1;
}

.form-group .input-unit span {
    font-size: .8rem;
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
}

.btn {
    display: block;
    width: 100%;
    padding: .85rem;
    background: linear-gradient(135deg, var(--secondary), var(--accent));
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-size: .9rem;
    font-weight: 700;
    font-family: var(--font);
    cursor: pointer;
    transition: opacity .2s, transform .15s, box-shadow .2s;
    -webkit-appearance: none;
}

.btn:active {
    transform: scale(.97);
}

.btn-secondary {
    background: var(--bg);
    color: var(--text);
}

.result-card {
    background: linear-gradient(135deg, #eff6ff, #ffffff);
    border: 2px solid var(--accent);
    border-radius: var(--radius);
    padding: 1.25rem;
}

.result-value {
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1.2;
}

.result-label {
    font-size: .72rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: .04em;
    font-weight: 600;
    margin-top: .15rem;
}

.result-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: .75rem;
}

@media (max-width: 480px) {
    .app-header { padding: 1rem 1.25rem; }
    .app-header h1 { font-size: 1.1rem; }
    .main-content { padding: .75rem; gap: .75rem; }
    .card { padding: 1rem; }
    .result-row { grid-template-columns: 1fr; }
}