/* ========== CSS Custom Properties ========== */
:root {
    --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark theme */
body.dark-mode {
    --bg-primary: #0c0c0f;
    --bg-secondary: #16161a;
    --bg-card: rgba(255, 255, 255, 0.04);
    --bg-card-border: rgba(255, 255, 255, 0.06);
    --bg-input: rgba(255, 255, 255, 0.06);
    --bg-input-focus: rgba(255, 255, 255, 0.1);
    --border-input: rgba(255, 255, 255, 0.1);
    --border-input-focus: rgba(99, 102, 241, 0.5);
    --text-primary: #f0f0f3;
    --text-secondary: #8b8b9e;
    --text-muted: #5a5a6e;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --accent-glow: rgba(99, 102, 241, 0.25);
    --result-bg: rgba(99, 102, 241, 0.08);
    --result-border: rgba(99, 102, 241, 0.2);
    --toggle-bg: rgba(255, 255, 255, 0.08);
    --toggle-hover: rgba(255, 255, 255, 0.12);
    --tag-bg: rgba(255, 255, 255, 0.06);
    --tag-text: #a0a0b8;
    --backdrop-dot: rgba(255, 255, 255, 0.03);
}

/* Light theme */
body.light-mode {
    --bg-primary: #f5f5f7;
    --bg-secondary: #ffffff;
    --bg-card: rgba(255, 255, 255, 0.8);
    --bg-card-border: rgba(0, 0, 0, 0.06);
    --bg-input: rgba(0, 0, 0, 0.03);
    --bg-input-focus: rgba(0, 0, 0, 0.05);
    --border-input: rgba(0, 0, 0, 0.1);
    --border-input-focus: rgba(99, 102, 241, 0.5);
    --text-primary: #1a1a2e;
    --text-secondary: #6b6b80;
    --text-muted: #9b9bae;
    --accent: #6366f1;
    --accent-hover: #4f46e5;
    --accent-glow: rgba(99, 102, 241, 0.2);
    --result-bg: rgba(99, 102, 241, 0.06);
    --result-border: rgba(99, 102, 241, 0.15);
    --toggle-bg: rgba(0, 0, 0, 0.05);
    --toggle-hover: rgba(0, 0, 0, 0.08);
    --tag-bg: rgba(0, 0, 0, 0.04);
    --tag-text: #6b6b80;
    --backdrop-dot: rgba(0, 0, 0, 0.03);
}

/* ========== Reset & Base ========== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font);
    transition: background-color var(--transition), color var(--transition);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    padding: 24px;
    padding-bottom: 60px;
}

/* Subtle dot grid background */
.backdrop {
    position: fixed;
    inset: 0;
    background-image: radial-gradient(var(--backdrop-dot) 1px, transparent 1px);
    background-size: 24px 24px;
    pointer-events: none;
    z-index: 0;
}

/* ========== Theme Toggle ========== */
#themeToggle {
    position: fixed;
    top: 20px;
    right: 20px;
    width: 44px;
    height: 44px;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--toggle-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--bg-card-border);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition);
    z-index: 100;
    font-size: 0;
}

#themeToggle:hover {
    background: var(--toggle-hover);
    color: var(--text-primary);
    transform: scale(1.05);
}

body.dark-mode .icon-moon,
body.light-mode .icon-sun {
    display: none;
}

body.dark-mode .icon-sun,
body.light-mode .icon-moon {
    display: block;
}

/* ========== Container ========== */
.container {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 480px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* ========== Header ========== */
.header {
    text-align: center;
    padding: 8px 0 4px;
}

.logo {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--accent), #a78bfa);
    border-radius: var(--radius-md);
    margin-bottom: 16px;
}

.logo-icon {
    font-size: 22px;
    font-weight: 700;
    color: #fff;
    letter-spacing: -0.5px;
}

h1 {
    font-size: 26px;
    font-weight: 700;
    letter-spacing: -0.5px;
    line-height: 1.2;
    margin-bottom: 6px;
}

.subtitle {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 400;
}

/* ========== Card ========== */
.card {
    background: var(--bg-card);
    border: 1px solid var(--bg-card-border);
    border-radius: var(--radius-xl);
    padding: 28px 24px;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    transition: background var(--transition), border-color var(--transition);
}

/* ========== Input Section ========== */
.input-section {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.input-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

label {
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    letter-spacing: 0.01em;
    transition: color var(--transition);
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

input {
    width: 100%;
    padding: 12px 14px;
    background: var(--bg-input);
    border: 1px solid var(--border-input);
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-family: var(--font);
    font-weight: 500;
    color: var(--text-primary);
    transition: all var(--transition);
    outline: none;
}

input::placeholder {
    color: var(--text-muted);
    font-weight: 400;
}

input:focus {
    background: var(--bg-input-focus);
    border-color: var(--border-input-focus);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.input-suffix {
    position: absolute;
    right: 12px;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-muted);
    pointer-events: none;
    transition: color var(--transition);
}

/* Pad input text to avoid overlapping suffix */
.input-wrapper input {
    padding-right: 60px;
}

.input-row .input-wrapper input {
    padding-right: 14px;
}

/* ========== APY Toggle ========== */
.apy-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

#toggleApyMode {
    padding: 4px 10px;
    font-size: 11px;
    font-weight: 500;
    font-family: var(--font);
    color: var(--tag-text);
    background: var(--tag-bg);
    border: 1px solid var(--bg-card-border);
    border-radius: 100px;
    cursor: pointer;
    transition: all var(--transition);
    letter-spacing: 0.02em;
}

#toggleApyMode:hover {
    background: var(--toggle-hover);
    color: var(--text-primary);
}

.end-apy-container {
    display: none;
    flex-direction: column;
    gap: 6px;
    margin-top: 8px;
    animation: slideDown 0.25s ease-out;
}

.end-apy-container.visible {
    display: flex;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ========== Calculate Button ========== */
.btn-calculate {
    width: 100%;
    padding: 14px;
    font-size: 15px;
    font-weight: 600;
    font-family: var(--font);
    color: #fff;
    background: linear-gradient(135deg, var(--accent), #818cf8);
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition);
    letter-spacing: 0.02em;
    margin-top: 4px;
}

.btn-calculate:hover {
    background: linear-gradient(135deg, var(--accent-hover), #6366f1);
    box-shadow: 0 4px 20px var(--accent-glow);
    transform: translateY(-1px);
}

.btn-calculate:active {
    transform: translateY(0);
}

/* ========== Result ========== */
.result {
    background: var(--result-bg);
    border: 1px solid var(--result-border);
    border-radius: var(--radius-lg);
    padding: 24px;
    text-align: center;
    display: none;
    transition: all var(--transition);
    animation: fadeInUp 0.35s ease-out;
}

.result.visible {
    display: block;
}

.result-label {
    font-size: 12px;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 6px;
}

.result-value {
    font-size: 28px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.result.error .result-value {
    font-size: 15px;
    font-weight: 500;
    color: #ef4444;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ========== Formula Section ========== */
.formula-section {
    text-align: center;
    padding: 8px 0;
}

.formula-label {
    font-size: 12px;
    color: var(--text-muted);
    margin-bottom: 12px;
    font-weight: 400;
}

.formula-img-wrapper {
    display: flex;
    justify-content: center;
}

.formula-img-wrapper img {
    max-width: 100%;
    height: auto;
    opacity: 0.7;
    border-radius: var(--radius-sm);
    transition: opacity var(--transition);
}

body.light-mode .formula-img-wrapper img {
    filter: invert(1);
}

.formula-img-wrapper img:hover {
    opacity: 1;
}

/* ========== Responsive ========== */
@media (max-width: 520px) {
    body {
        padding: 16px;
        align-items: flex-start;
        padding-top: 60px;
    }

    .card {
        padding: 20px 16px;
    }

    h1 {
        font-size: 22px;
    }

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

    .result-value {
        font-size: 24px;
    }
}

/* ========== Number Input Spinners ========== */
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    opacity: 0.3;
}

/* ========== Disclaimer ========== */
.disclaimer {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 100;
    padding: 10px 24px;
    background: var(--bg-secondary);
    border-top: 1px solid var(--bg-card-border);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    transition: background var(--transition), border-color var(--transition);
}

.disclaimer p {
    max-width: 720px;
    margin: 0 auto;
    font-size: 11px;
    line-height: 1.5;
    color: var(--text-muted);
    text-align: center;
}

/* ========== Selection ========== */
::selection {
    background: var(--accent);
    color: #fff;
}