:root {
    /* iOS Light Mode */
    --bg-system: #f2f2f7;
    --bg-grouped: #ffffff;
    --text-primary: #000000;
    --text-secondary: #8e8e93;
    --text-tertiary: #c7c7cc;
    --accent: #007aff;
    --separator: #c6c6c8;
    --nav-bg: rgba(242, 242, 247, 0.8);
    
    /* Apple Spring Easing */
    --spring: cubic-bezier(0.175, 0.885, 0.32, 1.1);
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

@media (prefers-color-scheme: dark) {
    :root {
        /* iOS Dark Mode */
        --bg-system: #000000;
        --bg-grouped: #1c1c1e;
        --text-primary: #ffffff;
        --text-secondary: #8e8e93;
        --text-tertiary: #48484a;
        --accent: #0a84ff;
        --separator: #38383a;
        --nav-bg: rgba(0, 0, 0, 0.75);
    }
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Icons", "Helvetica Neue", Helvetica, Arial, sans-serif;
    background-color: var(--bg-system);
    color: var(--text-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    min-height: 100vh;
    font-size: 17px;
    line-height: 1.3;
}

/* Typography Hierarchy */
h1, .display {
    font-size: 34px;
    font-weight: 700;
    letter-spacing: -0.04em;
    line-height: 1.2;
    margin-bottom: 24px;
}

h2 {
    font-size: 22px;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: 12px;
}

p {
    font-size: 17px;
    color: var(--text-secondary);
    letter-spacing: -0.02em;
    margin-bottom: 16px;
}

.subtitle {
    font-size: 15px;
    color: var(--text-secondary);
    letter-spacing: -0.01em;
    margin-bottom: 24px;
}

/* Layout */
.app-container {
    max-width: 100%;
    margin: 0 auto;
    padding-bottom: 60px;
}

@media (min-width: 768px) {
    .app-container {
        max-width: 600px;
        padding-top: 40px;
    }
}

/* Navigation Bar (Translucent Chrome) */
.toolbar {
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    justify-content: space-between;
    align-items: center;
    
    /* Edge-to-edge breakout */
    width: 100vw;
    margin-left: calc(50% - 50vw);
    padding: 12px calc(50vw - 50% + 16px);
    
    background: var(--nav-bg);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border-bottom: 0.5px solid var(--separator);
    margin-bottom: 24px;
}

.toolbar .right-items {
    display: flex;
    align-items: center;
    gap: 16px;
}

/* Navigation Buttons */
.nav-btn {
    background: transparent;
    border: none;
    color: var(--accent);
    font-size: 17px;
    font-weight: 400;
    cursor: pointer;
    padding: 4px 8px;
    transition: opacity 0.2s;
}

.nav-btn:active {
    opacity: 0.5;
}

/* Page Views */
.view {
    display: none;
    opacity: 0;
    padding: 0 16px;
}

.view.active {
    display: block;
    animation: fadeIn 0.4s var(--ease-out) forwards;
}

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

.hero {
    text-align: left;
    margin-bottom: 32px;
    padding-top: 16px;
}

/* iOS Inset Grouped Lists (The core structure) */
.card {
    background: var(--bg-grouped);
    border-radius: 12px;
    margin-bottom: 24px;
    padding: 0; /* padding is inside list items */
    overflow: hidden;
}

.list-item {
    display: flex;
    flex-direction: column;
    padding: 16px;
    border-bottom: 0.5px solid var(--separator);
}

.list-item:last-child {
    border-bottom: none;
}

/* Forms & Inputs */
input[type="text"], input[type="range"] {
    width: 100%;
    font-size: 17px;
    padding: 16px;
    border: none;
    background: transparent;
    color: var(--text-primary);
    outline: none;
}

input[type="text"]::placeholder {
    color: var(--text-tertiary);
}

.input-group {
    background: var(--bg-grouped);
    border-radius: 12px;
    margin-bottom: 24px;
    overflow: hidden;
}

.input-group input {
    border-bottom: 0.5px solid var(--separator);
}
.input-group input:last-child {
    border-bottom: none;
}

/* Primary iOS Buttons */
.btn {
    display: block;
    width: 100%;
    background: var(--bg-grouped);
    color: var(--accent);
    font-size: 17px;
    font-weight: 500;
    padding: 16px;
    border: none;
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    margin-bottom: 16px;
    transition: background-color 0.2s, transform 0.2s var(--ease-out);
}

.btn:active {
    background-color: var(--separator);
    transform: scale(0.98);
}

.btn.primary {
    background-color: var(--accent);
    color: #ffffff;
    font-weight: 600;
}

.btn.primary:active {
    background-color: var(--accent);
    opacity: 0.8;
}

.btn.secondary {
    background-color: transparent;
}

/* Interactive Janken Grid */
.janken-controls {
    display: flex;
    gap: 12px;
    margin-top: 16px;
}

.janken-btn {
    flex: 1;
    background: var(--bg-grouped);
    border: none;
    border-radius: 16px;
    font-size: 40px;
    padding: 32px 0;
    cursor: pointer;
    transition: transform 0.3s var(--spring), background-color 0.2s;
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}

@media (prefers-color-scheme: dark) {
    .janken-btn { box-shadow: none; }
}

.janken-btn:active:not(:disabled) {
    transform: scale(0.92);
    background-color: var(--separator);
}

.janken-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: scale(0.95);
}

.result-message {
    text-align: center;
    font-size: 17px;
    font-weight: 500;
    color: var(--accent);
    margin-top: 24px;
    min-height: 24px;
}

/* Badges */
.badge {
    background: var(--separator);
    color: var(--text-primary);
    padding: 2px 8px;
    border-radius: 10px;
    font-size: 13px;
    font-weight: 500;
}

/* Toasts (iOS Notification Style) */
.toast {
    position: fixed;
    top: 16px; /* iOS notifications drop from top */
    left: 50%;
    transform: translateX(-50%) translateY(0);
    background: rgba(28, 28, 30, 0.85);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    color: #ffffff;
    padding: 16px 24px;
    border-radius: 20px;
    font-size: 15px;
    font-weight: 500;
    z-index: 1000;
    box-shadow: 0 8px 24px rgba(0,0,0,0.15);
    transition: transform 0.5s var(--spring), opacity 0.5s var(--ease-out);
    display: flex;
    align-items: center;
    gap: 12px;
}

@media (prefers-color-scheme: dark) {
    .toast {
        background: rgba(44, 44, 46, 0.85);
    }
}

.toast.hidden {
    transform: translateX(-50%) translateY(-120%);
    opacity: 0;
    pointer-events: none;
}

/* Profile List Customization */
#credentials-list {
    margin-top: 24px;
}

.cred-item {
    background: var(--bg-grouped);
    border-radius: 12px;
    padding: 16px;
    margin-bottom: 12px;
    font-size: 14px;
}

.cred-item div {
    margin-bottom: 8px;
    color: var(--text-secondary);
}

.cred-item strong {
    color: var(--text-primary);
    font-weight: 600;
}

.mt-4 { margin-top: 32px; }

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    * {
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
    }
}