:root {
    --primary-color: #37474f; /* Blue Grey 800 - Low profile, professional */
    --accent-color: #546e7a;  /* Blue Grey 600 */
    --background-color: #eceff1; /* Blue Grey 50 */
    --card-bg: #ffffff;
    --text-primary: #212121;
    --text-secondary: #757575;
    --divider-color: #bdbdbd;
    --error-color: #d32f2f;
    --shadow-1: 0 2px 5px rgba(0,0,0,0.16), 0 2px 10px rgba(0,0,0,0.12);
    --shadow-2: 0 5px 15px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);
    --radius: 4px;
    --font-family: 'Roboto', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* App Bar */
.app-bar {
    background-color: var(--primary-color);
    color: white;
    padding: 16px;
    box-shadow: var(--shadow-1);
    display: flex;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.app-bar h1 {
    font-size: 20px;
    font-weight: 500;
    margin: 0;
}

/* Layout */
.container {
    max-width: 600px;
    margin: 20px auto;
    padding: 0 16px;
}

/* Cards */
.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow-1);
    padding: 16px;
    margin-bottom: 16px;
    transition: box-shadow 0.3s ease;
}

.card:hover {
    box-shadow: var(--shadow-2);
}

.card-title {
    font-size: 18px;
    color: var(--text-primary);
    margin-bottom: 8px;
    font-weight: 500;
}

.card-content {
    color: var(--text-secondary);
    font-size: 14px;
}

/* Forms */
.form-group {
    margin-bottom: 24px;
    position: relative;
}

.form-group label {
    display: block;
    font-size: 12px;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.form-control {
    width: 100%;
    padding: 8px 0;
    border: none;
    border-bottom: 2px solid var(--divider-color);
    background: transparent;
    font-size: 16px;
    color: var(--text-primary);
    transition: border-color 0.3s;
}

.form-control:focus {
    outline: none;
    border-bottom-color: var(--primary-color);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0 16px;
    height: 36px;
    line-height: 36px;
    border-radius: 2px;
    font-size: 14px;
    font-weight: 500;
    text-transform: uppercase;
    text-decoration: none;
    cursor: pointer;
    border: none;
    transition: background 0.3s, box-shadow 0.3s;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-1);
}

.btn-primary:hover {
    background-color: var(--accent-color);
    box-shadow: var(--shadow-2);
}

.btn-block {
    display: block;
    width: 100%;
    text-align: center;
}

/* Utilities */
.text-center { text-align: center; }
.mt-2 { margin-top: 16px; }
.text-error { color: var(--error-color); font-size: 14px; }
.hidden { display: none; }

/* Android-like List */
.resource-list {
    list-style: none;
    padding: 0;
}

.resource-item {
    background: white;
    border-bottom: 1px solid var(--divider-color);
    padding: 16px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.resource-info h3 {
    font-size: 16px;
    font-weight: 400;
    color: var(--text-primary);
}

.resource-info p {
    font-size: 12px;
    color: var(--text-secondary);
}