* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary: #0f766e;
    --primary-light: #14b8a6;
    --primary-dark: #0d5d56;
    --background: #f0fdfa;
    --foreground: #134e4a;
    --card: #ffffff;
    --card-foreground: #1f2937;
    --muted: #f3f4f6;
    --muted-foreground: #6b7280;
    --border: #e5e7eb;
    --accent: #ccfbf1;
    --success: #10b981;
    --radius: 12px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: linear-gradient(135deg, var(--background) 0%, #e0f7f4 100%);
    min-height: 100vh;
    color: var(--card-foreground);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 2.5rem;
}

.header h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--foreground);
    margin-bottom: 0.5rem;
}

.header p {
    color: var(--muted-foreground);
    font-size: 1rem;
}

/* Cards */
.card {
    background: var(--card);
    border-radius: var(--radius);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
    border: 1px solid var(--border);
    overflow: hidden;
}

.card-header {
    padding: 1rem 1.25rem 0.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.card-header h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--muted-foreground);
    text-transform: uppercase;
    letter-spacing: 0.025em;
}

.card-icon {
    font-size: 1.25rem;
}

.card-content {
    padding: 0.75rem 1.25rem 1.25rem;
}

/* Input Grid */
.input-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
    margin-bottom: 1rem;
}

/* Input Wrapper */
.input-wrapper {
    display: flex;
    align-items: center;
    background: var(--muted);
    border-radius: 8px;
    padding: 0.5rem 0.75rem;
    margin-bottom: 1rem;
    border: 2px solid transparent;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.input-wrapper:focus-within {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(15, 118, 110, 0.1);
}

.input-prefix,
.input-suffix {
    color: var(--muted-foreground);
    font-weight: 500;
    font-size: 0.9375rem;
}

.input-wrapper input {
    flex: 1;
    border: none;
    background: transparent;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--foreground);
    text-align: center;
    outline: none;
    width: 100%;
    min-width: 0;
}

.input-wrapper input::-webkit-outer-spin-button,
.input-wrapper input::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

.input-wrapper input[type=number] {
    -moz-appearance: textfield;
}

/* Range Slider */
input[type="range"] {
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--border);
    outline: none;
    -webkit-appearance: none;
    cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--primary);
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    transition: transform 0.15s, box-shadow 0.15s;
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
    box-shadow: 0 3px 6px rgba(0, 0, 0, 0.25);
}

input[type="range"]::-moz-range-thumb {
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--primary);
    cursor: pointer;
    border: none;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.range-labels {
    display: flex;
    justify-content: space-between;
    margin-top: 0.5rem;
    font-size: 0.75rem;
    color: var(--muted-foreground);
}

/* Frequency Card */
.frequency-card {
    margin-bottom: 1rem;
}

.frequency-options {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.frequency-btn {
    flex: 1;
    min-width: 120px;
    padding: 0.625rem 1rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    background: var(--card);
    color: var(--card-foreground);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.frequency-btn:hover {
    border-color: var(--primary-light);
    background: var(--accent);
}

.frequency-btn.active {
    border-color: var(--primary);
    background: var(--primary);
    color: white;
}

/* Chart Card */
.chart-card {
    margin-bottom: 1rem;
}

.chart-container {
    position: relative;
    height: 300px;
    width: 100%;
}

/* Results Grid */
.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.result-card {
    background: var(--card);
    border-radius: var(--radius);
    padding: 1.25rem;
    text-align: center;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--border);
}

.result-label {
    font-size: 0.875rem;
    color: var(--muted-foreground);
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.result-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--foreground);
}

.result-value.interest {
    color: var(--success);
}

.result-value.roi {
    color: var(--primary);
}

/* Footer */
.footer {
    text-align: center;
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
    color: var(--muted-foreground);
    font-size: 0.875rem;
}

/* Responsive */
@media (max-width: 640px) {
    .container {
        padding: 1rem;
    }

    .header h1 {
        font-size: 1.5rem;
    }

    .input-grid {
        grid-template-columns: 1fr;
    }

    .frequency-options {
        flex-direction: column;
    }

    .frequency-btn {
        min-width: 100%;
    }

    .results-grid {
        grid-template-columns: 1fr;
    }

    .result-value {
        font-size: 1.25rem;
    }

    .chart-container {
        height: 250px;
    }
}