:root {
    --bg-color: #f4f4f4;
    --card-bg: #ffffff;
    --text-color: #333333;
    --accent-color: #6943FF;
    --accent-text: #ffffff;
    --border-color: #dddddd;
    --input-bg: #ffffff;
    --hero-bg: #6943FF;
    --hero-text: #ffffff;
    --shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.dark-mode {
    --bg-color: #121212;
    --card-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --accent-color: #bb86fc;
    --accent-text: #000000;
    --border-color: #333333;
    --input-bg: #2c2c2c;
    --hero-bg: #1f1b24; /* Darker purple/grey */
    --hero-text: #ffffff;
    --shadow: 0 4px 6px rgba(0,0,0,0.5);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    transition: background-color 0.3s, color 0.3s;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 20px;
    background-color: var(--hero-bg);
    color: var(--hero-text);
}

h1 {
    margin: 0;
    font-size: 1.5rem;
}

#theme-toggle {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--hero-text);
}

#container {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
}

#hero {
    background-color: var(--hero-bg);
    width: 100%;
    padding: 40px 0;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    box-shadow: var(--shadow);
}

#user-input {
    font-size: 3rem;
    font-weight: bold;
    text-align: center;
    padding: 10px;
    width: 200px;
    border: 2px solid var(--accent-color);
    border-radius: 8px;
    background-color: var(--input-bg);
    color: var(--text-color);
    outline: none;
}

#user-input:focus {
    border-color: var(--accent-text);
    box-shadow: 0 0 10px var(--accent-color);
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

#cards-container {
    width: 100%;
    padding: 20px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    box-sizing: border-box;
}

.card {
    background-color: var(--card-bg);
    border-radius: 10px;
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    border: 1px solid var(--border-color);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 10px;
}

.card-title {
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--accent-color);
    margin: 0;
}

.unit-controls {
    display: flex;
    gap: 5px;
}

select {
    padding: 5px;
    border-radius: 5px;
    border: 1px solid var(--border-color);
    background-color: var(--input-bg);
    color: var(--text-color);
}

.swap-btn {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    cursor: pointer;
    color: var(--text-color);
    padding: 5px 8px;
}

.swap-btn:hover {
    background-color: var(--border-color);
}

.conversion-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
    padding: 10px;
    background-color: var(--bg-color);
    border-radius: 5px;
}

.conversion-text {
    font-size: 1.1rem;
    font-family: monospace;
    word-break: break-all;
}

.copy-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.2rem;
    margin-left: 10px;
    opacity: 0.5;
    transition: opacity 0.2s;
}

.copy-btn:hover {
    opacity: 1;
}

.ad-container {
    width: 100%;
    padding: 20px;
    text-align: center;
    background-color: var(--border-color);
    color: var(--text-color);
    margin: 10px 0;
    box-sizing: border-box;
}

.ad-placeholder {
    font-style: italic;
    color: #666;
}

footer {
    text-align: center;
    padding: 20px;
    margin-top: auto;
    background-color: var(--card-bg);
    border-top: 1px solid var(--border-color);
}

footer a {
    color: var(--accent-color);
    text-decoration: none;
}