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

body {
    min-height: 100vh;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
        sans-serif;
    display: flex;
    flex-direction: column;
}

/* Brand palette – LIGHT THEME DEFAULT VALUES */
:root {
    --yt-bg: #caf0f8;
    --yt-bg-gradient-top: #caf0f8;
    --yt-bg-gradient-bottom: #90e0ef;

    --yt-card-bg: #ffffff;
    --yt-card-soft: #f3fbff;

    --yt-text: #03045e;
    --yt-text-muted: #4b5670;

    --yt-border: #90e0ef;
    --yt-input-bg: #ffffff;

    --yt-accent: #0077b6;  /* main */
    --yt-accent-2: #00b4d8;
    --yt-accent-3: #03045e;

    --yt-shadow-soft: 0 14px 30px rgba(3, 4, 94, 0.12);
}

/* DARK THEME OVERRIDES */
body[data-theme="dark"] {
    --yt-bg: #03045e;
    --yt-bg-gradient-top: #03045e;
    --yt-bg-gradient-bottom: #0077b6;

    --yt-card-bg: rgba(0, 0, 0, 0.25);
    --yt-card-soft: rgba(0, 0, 0, 0.18);

    --yt-text: #fdfdfd;
    --yt-text-muted: #c4d7f5;

    --yt-border: rgba(144, 224, 239, 0.35);
    --yt-input-bg: rgba(3, 4, 94, 0.8);

    --yt-accent: #00b4d8;
    --yt-accent-2: #90e0ef;
    --yt-accent-3: #caf0f8;

    --yt-shadow-soft: 0 16px 40px rgba(0, 0, 0, 0.4);
}

/* Background */
body {
    background: radial-gradient(
        circle at top,
        var(--yt-bg-gradient-top),
        var(--yt-bg-gradient-bottom)
    );
    color: var(--yt-text);
}

/* Header */
.header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 20px;
    max-width: 1100px;
    width: 100%;
    margin: 12px auto 0;
    color: var(--yt-text);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo {
    width: 42px;
    height: 42px;
    border-radius: 13px;
    object-fit: cover;
    border: 2px solid var(--yt-accent-2);
    box-shadow: 0 0 0 3px rgba(0, 180, 216, 0.18);
}

.app-title {
    font-size: 1.35rem;
    font-weight: 700;
}

.subtitle {
    font-size: 0.8rem;
    color: var(--yt-text-muted);
}

/* Theme toggle */
.header-right {
    display: flex;
    align-items: center;
}

.mode-toggle {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background-color: var(--yt-card-bg);
    border-radius: 999px;
    padding: 4px 10px 4px 12px;
    border: 1px solid var(--yt-border);
    cursor: pointer;
    box-shadow: var(--yt-shadow-soft);
    transition: background-color 0.2s ease, transform 0.1s ease;
}

.mode-toggle:hover {
    transform: translateY(-1px);
}

.mode-label {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--yt-text-muted);
}

.mode-icon {
    font-size: 0.9rem;
}

.toggle-switch {
    width: 32px;
    height: 16px;
    border-radius: 999px;
    background: linear-gradient(90deg, var(--yt-accent-2), var(--yt-accent));
    position: relative;
    padding: 1px;
}

.toggle-knob {
    width: 14px;
    height: 14px;
    border-radius: 999px;
    background-color: #ffffff;
    box-shadow: 0 2px 5px rgba(3, 4, 94, 0.35);
    transform: translateX(0);
    transition: transform 0.2s ease;
}

/* Main layout */
.container {
    flex: 1;
    display: flex;
    flex-direction: column;
    max-width: 1100px;
    width: 100%;
    margin: 0 auto;
    padding: 0 16px 16px;
    gap: 16px;
}

/* Controls */
.controls {
    margin-top: 4px;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    background-color: var(--yt-card-bg);
    border-radius: 18px;
    padding: 12px;
    border: 1px solid var(--yt-border);
    box-shadow: var(--yt-shadow-soft);
}

.control-group {
    flex: 1;
    min-width: 150px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.control-group label {
    font-size: 0.8rem;
    color: var(--yt-text-muted);
}

.control-group select {
    padding: 8px 10px;
    border-radius: 10px;
    border: 1px solid var(--yt-border);
    background-color: var(--yt-input-bg);
    color: var(--yt-text);
    outline: none;
    font-size: 0.85rem;
}

/* Chat */
.chat-box {
    display: flex;
    flex-direction: column;
    background-color: var(--yt-card-bg);
    border-radius: 18px;
    border: 1px solid var(--yt-border);
    box-shadow: var(--yt-shadow-soft);
    min-height: 380px;
    overflow: hidden;
}

.chat-window {
    flex: 1;
    padding: 16px;
    overflow-y: auto;
    max-height: 65vh;
    background: radial-gradient(
            circle at top left,
            rgba(0, 180, 216, 0.12),
            transparent
        ),
        radial-gradient(
            circle at bottom right,
            rgba(144, 224, 239, 0.12),
            transparent
        );
}

/* Messages */
.msg {
    max-width: 80%;
    padding: 10px 12px;
    border-radius: 14px;
    margin-bottom: 10px;
    line-height: 1.5;
    font-size: 0.9rem;
    word-wrap: break-word;
}

.msg.user {
    margin-left: auto;
    background: linear-gradient(135deg, var(--yt-accent), var(--yt-accent-2));
    color: #ffffff;
    box-shadow: 0 6px 12px rgba(0, 119, 182, 0.4);
}

.msg.ai {
    margin-right: auto;
    background-color: var(--yt-card-soft);
    border: 1px solid rgba(144, 224, 239, 0.6);
    color: var(--yt-text);
}

/* Chat form */
.chat-form {
    display: flex;
    gap: 8px;
    padding: 10px;
    border-top: 1px solid var(--yt-border);
    background-color: var(--yt-card-bg);
}

.chat-form textarea {
    flex: 1;
    resize: none;
    border-radius: 12px;
    border: 1px solid var(--yt-border);
    padding: 8px 10px;
    background-color: var(--yt-input-bg);
    color: var(--yt-text);
    font-size: 0.9rem;
    outline: none;
}

.chat-form button {
    padding: 0 20px;
    border-radius: 12px;
    border: none;
    background: linear-gradient(135deg, var(--yt-accent), var(--yt-accent-2));
    color: #ffffff;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.08s ease, box-shadow 0.08s ease, opacity 0.1s;
    box-shadow: 0 6px 12px rgba(0, 119, 182, 0.5);
}

.chat-form button:hover:not(:disabled) {
    transform: translateY(-1px);
    box-shadow: 0 10px 18px rgba(0, 119, 182, 0.6);
}

.chat-form button:disabled {
    opacity: 0.6;
    cursor: default;
}

/* Footer */
.footer {
    text-align: center;
    font-size: 0.75rem;
    padding: 10px;
    color: var(--yt-text-muted);
}

/* Responsive */
@media (max-width: 768px) {
    .header {
        padding: 10px 12px;
    }

    .container {
        padding: 0 10px 12px;
    }

    .controls {
        padding: 10px;
        border-radius: 14px;
    }

    .chat-box {
        border-radius: 14px;
    }

    .chat-window {
        max-height: 60vh;
    }
}

@media (max-width: 520px) {
    .header {
        flex-direction: column;
        align-items: flex-start;
        gap: 8px;
    }

    .app-title {
        font-size: 1.15rem;
    }

    .chat-form {
        flex-direction: column;
    }

    .chat-form button {
        width: 100%;
        height: 40px;
    }

    .msg {
        max-width: 100%;
    }
}